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  • 1
    ISSN: 1432-1106
    Keywords: Stance perturbation ; Cerebral potential ; Leg muscle e.m.g. response ; Spinal reflexes ; Motor control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to investigate the neuronal mechanisms underlying the compensatory movements following stance disturbance, leg muscle e.m.g. responses and cerebral potentials evoked by a treadmill acceleration impulse were analysed. It was found that the displacement was followed by a cerebral potential of a latency of 40–45 ms and EMG responses in the calf muscles at a latency of 65–70 ms. The e.m.g. responses represented specific compensatory reactions to the mode of perturbation (with a gastrocnemius activation following positive acceleration but a tibialis ant. activation following negative acceleration). The cerebral potentials, however, showed a common pattern to both conditions. In addition, the leg muscle e.m.g. reactions were not altered by learning effects and by forewarning of displacement onset, while the amplitude of the cerebral potentials was significantly smaller in these conditions compared to those produced in response to randomly induced perturbations. It was therefore concluded that the leg muscle e.m.g. reactions are mediated by a polysynaptic spinal reflex pathway which depends on a supraspinal control. The cerebral potentials seem to represent afferent signals which can be supposed to be subjected to modification and processing by supraspinal motor centres, according to the actual requirements.
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  • 2
    ISSN: 1432-1106
    Keywords: Vestibulo-spinal reflexes ; Motor control ; Regulation of stance and gait ; Head tilt ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Sudden tilts of the head to the front or rear were induced during stance, balancing, gait and during perturbations of gait. The most prominent response in the leg muscle electromyogram (e.m.g.) to head tilt occurred in the tibialis anterior muscle (latency about 55 ms) following a backward tilt induced during balancing. During stance and gait, the e.m.g. activity related to head tilt was only a minor component of the leg muscle activity normally occurring during gait. When the head tilt was induced shortly after a perturbation of gait (treadmill acceleration impulse), the compensatory reaction in the leg muscles did not significantly differ from that seen after the gait perturbation alone. In addition, the rate of acceleration of the head was tested against the compensatory e.m.g. responses: No correlation of influence could be discerned. The results indicate that sudden head tilts and the resulting head acceleration have little influence on the e.m.g. patterns that occur during gait and perturbations of gait. It is assumed that these patterns are regulated by central programs, and that the compensation for leg perturbation is achieved mainly by spinal reflex mechanisms. It is discussed whether the lack of head tilt responses is the result of an antagonistic vestibularneck interaction, or whether it indicates a reduced effectiveness of vestibulo- and cervico-spinal reflexes during gait.
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  • 3
    ISSN: 1432-1106
    Keywords: Stance and gait perturbation ; Cerebral potential ; Leg muscle e.m.g. response ; Spinal and transcortical reflexes ; Motor control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cerebral potentials (c.p.) evoked by electrical stimulation of the tibial nerve during stance and in the various phases of gait of normal subjects were compared with the c.p. and leg muscle e.m.g. responses evoked by perturbations of stance and gait. Over the whole step cycle of gait the c.p. evoked by an electrical stimulus were of smaller amplitude (3 μV and 9 μV, respectively) than that seen in the stance condition, and appeared with a longer latency (mean times to first positive peak: 63 and 43 ms, respectively). When the electrical stimulus was applied during stance after ischaemic blockade of group I afferents, the c.p. were similar to those evoked during gait. The c.p. evoked by perturbations were larger in amplitude than those produced by the electrical stimulus, but similar in latencies in both gait and stance (mean 26 μV and 40 μV; 65 ms and 42 ms, respectively) and configurations. The large gastrocnemius e.m.g. responses evoked by the stance and gait perturbations arose with a latency of 65 to 70 ms. Only in the stance condition was a smaller, shorter latency (40 ms) response seen. It is concluded that during gait the signals of group I afferents are blocked at both segmental and supraspinal levels which was tested by tibial nerve stimulation. It is suggested that the e.m.g. responses induced in the leg by gait perturbations are evoked by group II afferents and mediated via a spinal pathway. The c.p. evoked during gait most probably reflect the processing of this group II input by supraspinal motor centres for the coordination of widespread arm and trunk muscle activation, necessary to restablish body equilibrium.
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  • 4
    ISSN: 1432-2234
    Keywords: Substituted polymethines ; Energy spectrum of ∼ ; Complex substituents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is shown that upon substitution of polymethines R-(CH)N-R with complex many-atom substitution R-, in the energy gap of polymethine chains (N → ∞) may arise states which are responsible for longest-wavelength transition. For certain substituents the energy of the electron transitions may be considerably lower than 1 eV, i.e. the transitions may be in the near infra-red.
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  • 5
    ISSN: 1433-0350
    Keywords: Infection of the CNS ; Intracranial hypertension ; Pediatric brain abscess
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The authors review 10 years' experience in managing brain abscess in childhood: 19 cases were treated in children from 1 to 18 years old. The etiology was rhinogenic in 5 cases, congenital heart disease in 5, hematogenous in 3, traumatic in 3, postoperative in 1, and unknown in 3 cases. Brain abscesses that developed by direct spread were located nearby the source, whereas metastatic abscesses (such as cardiogenic or hematogenous) in most cases spread via the vertebral-basilar system, usually developing in the parieto-occipital regions. Four of the 5 cases with multiple abscesses were cardiogenic and one hematogenous. The most important neurological signs were paresis (10 cases) and cranial nerve involvement (10 cases). Six abscesses were sterile and 6 grew aerobic and 6 anaerobic bacteria. In one case, aerobic as well as anaerobic bacteria were found. Fifteen patients were treated preoperatively with antibiotics. The treatment was operative in 17 cases. In two cases, gravely ill on admission, no surgical treatment was given. The etiology, localization, bacteriology, surgical methods, and results in those cases are discussed.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 92 (1988), S. 19-28 
    ISSN: 0942-0940
    Keywords: Anterior choroidal artery ; anatomical vascular perfusion ; selective amygdalo-hippocampectomy ; temporo-medial region
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The anterior choroidal artery (A.ch.a.) was studied in 140 hemispheres of the human brain. In 50 specimens the artery was cannulated and perfused with acrylic resin, in 20 specimens the A.ch.a., was selectively cannulated and perfused with dye. The artery then was microsurgically dissected and photographically documented. The site of origin of the A.ch.a., its length, outer diameter, course, branching patterns, anastomoses, and areas of supply was recorded. The surgical and diagnostic significance of the A.ch.a. and its importance during surgical procedures are discussed.
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  • 7
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Summary Two mathematical models are considered which generate multimodal interval distributions. They may be applied for the description of interval distributions of unitary discharges of single neurons.
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  • 8
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
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  • 9
    ISSN: 1432-0711
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 10
    ISSN: 1432-0711
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Drei Frauen unter der Geburt wird eine titrierte Initialdosis (TID) von131J-Streptokinase innerhalb 1 min intravenös inkorperiert. Die Distribution erreicht ihr Maximum nach 3 min. Es wird danach eine Anreicherung der Substanz über der Leber mit einem Gipfel der Aktivität um 20 min nach Injektion gemessen. Zur gleichen Zeit ist im Blut höchste Fibrinolyseaktivität nachweisbar. Ein Placentatransfer von131J-Streptokinase wird von weniger als 1/1000 der mütterlichen Blutaktivität im Nabelschnurblut gemessen. Später im fetalen Blut auftretende Reaktionen werden durch passiven Übertritt von split products veranlaßt. Eine Thrombolysebehandlung mit Streptokinase während der Schwangerschaft ist demnach möglich. Erfahrungen an 12 selbstbehandelten Graviden liegen bisher vor.
    Notes: Summary A titrated initial dose (TID) of131J-streptokinase is injected intravenously into three women under labour within 1 minute. The distribution reaches its maximum after 3 minutes. The substance accumulates in the liver with a peak 20 minutes following injection. At the same time highest activity of fibrinolysis can be shown in blood. A placental transfer of131J-streptokinase less than 1/1000 of the activity in maternal blood can be demonstrated by analysis of cord blood. Reactions in fetal blood occuring after a larger time interval are caused by passive diffusion of split products. Hence a thrombolytic treatment with streptokinase is possible during pregnancy. There is some experience with 12 pregnant women of our clinic.
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