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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 113 (1991), S. 8384-8388 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 251-254 (Oct. 1997), p. 475-482 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1420-908X
    Keywords: Key words: Neutrophils – Chemokines – Carrier proteins –α2-Macroglobulin receptors – Alveolar macrophages
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: Objective and Design: The purpose of this study was to compare chemotactic activity of IL-8 alone with that of IL-8 reacted with rabbit α-macroglobulins (αM) in vivo.¶Methods: Initially the binding of recombinant human IL-8 (rhIL-8) to rabbit αM was studied. 125I-labeled rhIL-8 was incubated with αM, and electrophoresed on native 5% gels or SDS-polyacrylamide 4-20% gradient gels. Next, rhIL-8 or rhIL-8 bound to αM was administered via an endotracheal tube to rabbit's lungs.¶Treatment: An endotracheal tube was wedged into a segment of the lobe of each lung, and a sample instilled through the tube into this segment. After 4 h the lungs were lavaged.¶Results: rhIL-8 bound to αM retained its full chemotactic activity in vitro but exhibited a diminished ability to induce the influx of neutrophils into the rabbit lung.¶Conclusions: The data suggest that αM may facilitate IL-8 clearance from the lung.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1420-908X
    Keywords: Interleukin-8 ; Inhibitor ; Sepsis ; Neutrophils ; Lung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Staphylococcal enterotoxin A (SEA) is a superantigen, produced by some strains ofStaphylococcus aureus (S. aureus), which can cause a variety of clinical manifestations ranging from food poisoning to shock. SEA can also stimulate human alveolar macrophages to produce interleukin-8 (IL-8), a member of the α-chemokine subfamily that activates and is chemotactic for neutrophils. In these studies we showed that in rabbits, intravenous SEA significantly decreased the circulating white blood cell population from a baseline value of 6409±2027×103 cells/ml to 1943±862×103 cells/ml in 7 h. There was a concommitent increase in IL-8 in the circulating plasma (baseline: 60±34 pg/ml, 7 h post SEA: 109±64 pg/ml). The increase in circulating IL-8 was accompanied by a much greater increase in the IL-8 concentration of the epithelial lining fluid (ELF) where the IL-8 increased from 0.05±0.08 ng/ml (control) to 13.8±9.3 ng/ml (SEA treated). The increase in IL-8 concentration in the alveolar spaces was paralleled by an increase in both the percentage of neutrophils (1.4±0.9% (control) to 26.0±10.8% (SEA treated)) and total number of neutrophils (0.04±0.02×106/ml (control) to 4.8±3.3 106/ml (SEA treated)) in the airspaces, and the numbers of neutrophils in the ELF correlated with the IL-8 concentration r=0.62, p=0.006). When antileukinate, a hexapeptide which inhibits the binding of IL-8 to neutrophils, was administered to animals receiving SEA, the IL-8 concentration in the ELF (14.8±10.7 ng/ml) was not significantly different from the concentration of IL-8 in those animals receiving SEA alone). However, both the percentage of neutrophils (9.5±3.2%), and the total number of neutrophils (1.3±1.0×106/ml) in the ELF following SEA and antileukinate administration was significantly lower than in animals which only received SEA (p〈0.05). The findings suggest that SEA released into the circulation during a Staphylococcal infection can cause an inflammatory reaction in the lung. Since this reaction is at least partially mediated by IL-8, antileukinate may have pharmacologic potential in reducing the inflammatory reaction.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Intensive care medicine 20 (1994), S. 508-510 
    ISSN: 1432-1238
    Keywords: Trauma ; Immunity ; Pediatrics ; Immunoglobulins ; IgG subclasses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective To study immunoglobulin production after severe blunt head trauma in children. Design Serum for IgG, IgM, IgA, IgE, and IgG subclasses were drawn from 10 children admitted with severe head injury (ISS 31.2, GCS 5.4) on day 1, 7, 14 and 21 after injury. Results 5 of the 10 patients developed infection between 7 and 14 days and 2 died of complications of pneumonia. On day 1, IgM levels averaged 95.6% of the mean of the age-specific normal controls. By day 7, IgM levels averaged 383% (p〈0.01). While all patients were within the age-specific normal range (± 2 SD) on day 1, 7 of 10 patients were above the normal range by day 7. There was no difference in IgM levels between infected and non-infected patients. Five patients were below the age-specific normal range for IgG on day 1, with 3 still low on day 7. By day 21, IgG levels averaged 141% of the mean of the age-specific normal controls. IgG subclasses followed a pattern similar to total IgG levels. Marked increases in IgE were seen in 3 patients. Conclusions IgM levels increased dramatically in all patients within seven days of the injury. While 50% of these children had a deficit of IgG in the first week, total IgG and IgA levels increased after injury, but not as rapidly as IgM levels. Unlike pediatric burn patients, there is no persistent hypogammaglobulinemia following severe blunt trauma in children.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The primary function of the vestibuloocular reflex (VOR) is to maintain the stability of retinal images during head movements. This function is expressed through a complex array of dynamic and adaptive characteristics whose essential physiological basis is a disynaptic arc. We present a model of normal VOR function using a simple neural network architecture constrained by the physiological and anatomical characteristics of this disynaptic reflex arc. When tuned using a method of global optimization, this network is capable of exhibiting the broadband response characteristics observed in behavioral tests of VOR function. Examination of the internal units in the network show that this performance is achieved by rediscovering the solution to VOR processing first proposed by Skavenski and Robinson (1973). Type I units at the intermediate level of the network possess activation characteristics associated with either pure position or pure velocity. When the network is made more complex either through adding more pairs of internal units or an additional level of units, the characteristic division of unit activation properties into position and velocity types remains unchanged. Although simple in nature, the results of our simulations reinforce the validity of bottom-up approaches to modeling of neutral function. In addition, the architecture of the network is consistent with current ideas on the characteristics and site of adaptation of the reflex and should be compatible with current theories regarding learning rules for synaptic modification during VOR adaptation.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 67 (1992), S. 103-112 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The vestibulo-ocular reflex (VOR), which stabilizes the eyes in space during head movements, can undergo adaptive modification to maintain retinal stability in response to natural or experimental challenges. A number of models and neural sites have been proposed to account for this adaptation but these do not fully explain how the nervous system can detect and correct errors in both gain and phase of the VOR. This paper presents a general error correction algorithm based on the multiplicative combination of three signals (retinal slip velocity, head position, head velocity) directly relevant to processing of the VOR. The algorithm is highly specific, requiring the combination of particular sets of signals to achieve compensation. It is robust, with essentially perfect compensation observed for all gain (0.25X–4.0X) and phase (-180°–+180°) errors tested. Output of the model closely resembles behavioral data from both gain and phase adaptation experiments in a variety of species. Imposing physiological constraints (no negative activation levels or changes in the sign of unit weights) does not alter the effectiveness of the algorithm. These results suggest that the mechanisms implemented in our model correspond to those implemented in the brain of the behaving organism. Predictions concerning the nature of the adaptive process are specific enough to permit experimental verification using electrophysiological techniques. In addition, the model provides a strategy for adaptive control of any first order mechanical system.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 75 (1996), S. 309-319 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract.  We present a controls systems model of horizontal-plane head movements during perturbations of the trunk, which for the first time interfaces a model of the human head with neural feedback controllers representing the vestibulocollic (VCR) and the cervicocollic (CCR) reflexes. This model is homeomorphic such that model structure and parameters are drawn directly from anthropomorphic, biomechanical and physiological studies. Using control theory we analyzed the system model in the time and frequency domains, simulating neck movement responses to input perturbations of the trunk. Without reflex control, the head and neck system produced a second-order underdamped response with a 5.2 dB resonant peak at 2.1 Hz. Adding the CCR component to the system dampened the response by approximately 7%. Adding the VCR component dampened head oscillations by 75%. The VCR also improved low-frequency compensation by increasing the gain and phase lag, creating a phase minimum at 0.1 Hz and a phase peak at 1.1 Hz. Combining all three components (mechanics, VCR and CCR) linearly in the head and neck system reduced the amplitude of the resonant peak to 1.1 dB and increased the resonant frequency to 2.9 Hz. The closed loop results closely fit human data, and explain quantitatively the characteristic phase peak often observed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 36 (1979), S. 1-20 
    ISSN: 1432-1106
    Keywords: Reticulospinal ; Excitation ; Inhibition ; Axial motoneurons ; Limb motoneurons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Responses of motoneurons supplying muscles of the forelimbs, hindlimbs, back, and neck to stimulation of the medial pontomedullary reticular formation were studied with intracellular recording in cere-bellectomized cats under chloralose anesthesia. Stimulation of the midline or of a reticular region consisting of nucleus reticularis (n.r.) pontis caudalis and the dorsorostral part of n.r. gigantocellularis produced monosynaptic excitation of ipsilateral motoneurons supplying axial muscles and flexor and extensor muscles in both proximal and distal parts of the limbs. This widespread excitation appears to have been produced by rapidly conducting medial reticulospinal fibers. Stimulation of a second region consisting of n.r. ventralis and the ventrocaudal part of n. r. gigantocellularis produced monosynaptic excitation of ipsilateral neck and back motoneurons but only longer latency, apparently multisynaptic excitation of limb motoneurons. Collision tests indicated that this monosynaptic excitation did not involve fibers descending along the midline. It therefore appears to have been produced by lateral reticulospinal fibers. Reticular stimulation also produced short latency, monosynaptic inhibition of neck motoneurons, long latency, apparently polysynaptic inhibition of limb motoneurons and intermediate latency inhibition of back motoneurons. The latencies and properties of inhibitory responses of back motoneurons indicated that they were produced either disynaptically by fast fibers or monosynaptically by slower fibers. The data indicate that the medial pontomedullary reticular formation can be divided into a number of different zones each with a distinct pattern of connections with somatic motoneurons. These include the dorsorostrally located medial reticulospinal projection area, from which direct excitation of a wide variety of motoneurons can be evoked, the ventrocaudally located lateral reticulospinal projection area from which direct excitation of neck and back and direct inhibition of neck motoneurons can be evoked and the dorsal strip of n.r. gigantocellularis which has direct excitatory and inhibitory actions only on neck motoneurons.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1106
    Keywords: Vestibulo-ocular reflex ; Adaptation ; Gravity sense ; Otolith organs ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The specificity of adaptation of vestibuloocular reflex direction was examined by exposing cats to combined pitch vestibular rotation and horizontal optokinetic motion at 0.25 Hz, while alternating body position between lying on the left side and lying on the right. The direction of optokinetic motion relative to head motion was reversed when the cat's body posture was changed so that, for example, if head upward rotation was coupled to leftward visual world motion when the cat was lying on its left side, then head upward rotation was coupled to rightward visual world motion when the cat was on its right side. Body position and optokinetic motion direction were changed every 10 min for a total of 2 h of adaptation on each side. Horizontal and vertical electrooculographic recordings were made during pitch rotations in darkness before and after adaptation. Saccades were removed from the records and vestibulo-ocular reflex gain was measured in the direction of optokinetic motion. In every case, the adaptation procedure produced a directional change in the vestibulo-ocular reflex specific to the posture during measurement and appropriate to reduce the retinal image motion caused by the combined vestibular and optokinetic stimuli. That is, adaptive horizontal eye movements measured on the two sides were in opposite directions for the same direction of head motion. This specificity suggests that adaptation of vestibulo-ocular reflex direction involves specific neural pathways that are controlled by body orientation signals which most likely arise from the otolith organs.
    Type of Medium: Electronic Resource
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