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  • 1
    ISSN: 1432-1106
    Keywords: Posture ; Movement precuing ; Cerebellar disease ; Parkinson's disease ; Motor control ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Automatic postural responses of leg muscles to the sudden displacement of standing support were investigated under four different conditions of information given to subjects in advance. Results from three groups of subjects were compared: 6 normal subjects, 10 patients with cerebellar disease, and 9 patients with Parkinson's disease. Specifically, each subject was provided with visual information about the direction and/or the amplitude of an upcoming platform tilt. For the control situation no advance information on the characteristics of platform tilt was provided. Neither the latencies nor the integrals of postural EMG-responses showed alterations with advance information. In contrast, in a control experiment in which 3 normal subjects had to perform large or small forward or backward voluntary movements of the body around the ankle joint, shorter onset-latencies of leg muscle EMG responses were observed with increasing complexity of the advance information. These results suggest that, unlike voluntary movements, postural responses to rapid surface tilts do not benefit from advance visual information on direction or amplitude of a postural disturbance.
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  • 2
    ISSN: 1432-1106
    Keywords: Cutaneous reflexes ; Long-Latency reflexes ; Precision grip ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Hand muscle reflexes following muscle stretch and electrical nerve stimulation show a typical pattern consisting of short- and long-latency reflexes. The present investigation was designed to test reflexes following pure cutaneous stimulation. Air puffs were delivered to the palmar tip and the nail bed of the first, second and fifth fingers during isotonic contraction of hand muscles. The EMGs from the thenar muscles, the first dorsal interosseous muscle and the hypothenar muscles were recorded. Reflexes were obtained in all muscles, with a typical configuration consisting of a short-latency excitatory component (cutaneous longlatency reflex I, cLLR I) and a second excitatory component (cutaneous long-latency reflex II, cLLR II), with an inhibitory component between them. The size of cLLR II differed depending on the area stimulated and the muscle recorded. We found the largest responses always in the muscle acting on the stimulated finger. The reflex size depended on the strength of air puff stimulation. Allowing small displacements of the fingers led to an additional increase in the size of the reflex. The pattern of reflexes was identical independent of whether the finger tip or the nail bed was stimulated, but the size of the reflexes was smaller following nail bed stimulation. Following blockade of the cutaneous nerve branches of the thumb with local anaesthetics, air puff stimulation of the thumb no longer elicited this reflex pattern. Hence, under our experimental conditions, cutaneous receptors were the only source of afferent input for these reflexes. The results suggest that these cutaneous reflexes are mainly dedicated to controlling the stimulated finger independent of whether the palmar tip or the nail bed is stimulated. A possible physiological function is the adapting of grip force during handling of delicate objects if a perturbation is applied either to the object or the hand.
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  • 3
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Early reactions of rRNA-cistrons in lectin-stimulated PBL cultures of domestic pigs are shown. Interphases showing 3 or more clusters of stained areas were attributed mainly to cells after first division. Clear differences are shown between PHA-and ConA-induced NOR-expression patterns compared to the patterns in PW-stimulated cultures.
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  • 4
    ISSN: 1619-1560
    Keywords: carbon dioxide ; sympathetic activity ; humans ; cardiovascular regulation ; autonomic failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In vivo studies selectively assessing preganglionic and central autonomic nervous system activity in patients with autonomic failure have so far been limited to testing pituitary function. In animal experiments carbon dioxide (CO2) selectively stimulates central sympathetic nuclei in the ventrolateral medulla and preganglionic sympathetic neurons in the cervical trunk. This central stimulation seems to overrule less pronounced peripheral vasodilatatory effects. This study addressed the question of whether hypercapnea is a suitable challenge procedure to test preganglionic and central autonomic activity in healthy subjects and in patients with autonomic failure of preganglionic and central origin. Seven patients with multiple system atrophy (MSA) and 30 age-matched healthy volunteers underwent a protocol including a Valsalva manoeuvre (VM) under normo- and hypercapnic conditions and exposure to hypercapnea under supine resting conditions. Blood pressure (BP), heart rate (HR) and end-tidal CO2 partial pressure were measured continuously and non-invasively. In normal controls hypercapnea induced significantly higher BP values in phases II, IIe, III and IV of the VM compared to the normocapnic VM and a significant increase in BP during steady-state supine exposure compared to normocapnic baseline. HR increased significantly only after 40 s of steady-state hypercapnea during the latter challenge. In patients with MSA and autonomic failure, in whom a predominantly preganglionic lesion of the autonomic nervous system is established, no significant effects of hypercapnea on the cardiovascular parameters were found. Although this non-invasive challenge procedure cannot differentiate between pre- and postganglionic autonomic failure, exposure to hypercapnea enables the investigation of efferent autonomic activity to vasoconstrictors generated from autonomic centres in the brainstem and cervical trunk.
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  • 5
    ISSN: 1432-1459
    Keywords: Long-latency reflexes ; Mechanically evoked cortical potentials ; Somatosensory evoked potentials ; Transcranial magnetic stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Twenty-two patients with localized lesions of the central nervous system (unilateral cerebral ischaemia, cervical myelopathy, spinal tumour, familial spastic paraplegia) underwent neurophysiological evaluation of sensorimotor deficits of the leg. Functional methods using muscle stretch as stimulus, i.e. long-latency muscle responses and cortical potentials evoked by dorsiflection of the foot, were compared with transcranial magnetic stimulation and somatosensory evoked cortical potentials following electrical stimulation of the posterior tibial nerve. The functional neurophysiological methods yielded no diagnostic superiority with respect to the procedures using artificial (i.e. magnetic and electrical) stimulation. However, in most cases of missing compound motor action potentials following transcranial magnetic stimulation or missing electrically evoked cortical potentials, the long-latency muscle responses still allowed quantitative assessment of sensorimotor function.
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  • 6
    ISSN: 1432-1459
    Keywords: Hemiparesis ; Posture ; Voluntary movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Postural adjustments associated with the task of raising oneself on tiptoes were investigated in a reaction time paradigm in six normal subjects and six patients with hemiparesis due to stroke. Body and ankle position in space were measured by means of a movement analysis system (ELITE). The findings indicate that the task of going up on tiptoes is performed in two steps. First, the centre of gravity is shifted forward to a position per pendicular to the forefoot. This movement is initiated by a phasic burst of EMG activity in the tibialis anterior (TA). The activity of the quadriceps femoris (QUA) aids the forward shift and together with the biceps femoris (BF) stabilizes the knee. Following these postural adjustments, the action of going up on tip-toes is performed mainly by the gastrocnemius medialis (MG). The basic pattern of preparatory (TA, QUA, BF) and focal (MG) activity was disturbed in its temporal sequence in patients with hemiparesis. The analysis of the biomechanical data showed smaller movement velocities for leaning forward and going up on tiptoes in patients, with increased duration of going up on tiptoes and decreased movement amplitude on the paretic side. In addition, the correlation between the start of horizontal (leaning forward) and vertical (going up on tiptoes) hip movement was lost in patients. The preserved correlation between the latency of MG activity and the onset of the vertical hip movement on the paretic side in patients and the loss of correlation on the non-paretic side indicates that the EMG activity on the healthy side is adapted to the functional requirements of the affected side. The findings demonstrate that preparatory and executional activity are not programmed as a unit, but are more likely to be generated by a hierachically organized structure using proprioceptive and exteroceptive feedback.
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  • 7
    ISSN: 1432-1459
    Keywords: Alcoholic atrophy ; Alcohol abstinence ; Posturography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Postural instability was measured and short, medium and long latency EMG responses to angular displacement of the ankle were recorded from leg muscles in a group of 17 alcoholics who presented with clinical signs of cerebellar atrophy of the anterior lobe. Recordings were performed twice (average interval 18.5 months) to determine the effects of continued drinking versus abstinence on the signs of the cerebellar damage. Patients who were abstinent (n=11) exhibited a significant, sometimes dramatic decrease of body sway whereas patients who continued drinking (n=6) showed increased body sway when the eyes were closed. Short and medium latency EMG responses were unaltered in both groups of patients. The integral of the long latency response of the antagonist tended to increase with continued abuse and to decrease in abstinent patients.
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