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  • 1
    ISSN: 1615-6714
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Compliance with wearing removable appliances cannot be determined directly from progress noted in the course of treatment. The orthodontist’s judgement is influenced by many and varied observations and the evidence they yiel is often unclear. We studied 104 orthodontic patients aged nine to 16 years using as data treatment records, provider and patient questionnaires, and oral hygiene indexes. In addition theLuescher psychological color test was administered to a subgroup and the duration of compliance wear was objectively measured. We found little consistency among different compliance indicators. Studying the patient’s keeping of appointments, his oral hygiene habits, and appliance maintenance did not result in general conclusions pertaining to the patient’s compliance with wearing the appliance. Only over a longer period it is possible to determination clinical observation the patient’s cooperation in his treatment. More promising on the other hand for patient compliance behavior is the combination of information obtained clinically with the through psychological tests.
    Notes: Zusammenfassung Das Trageverhalten bei herausnehmbaren Geräten läßt sich nicht jederzeit linear aus dem Behandlungsfortschrift erschließen. In das Urteil des Kieferorthopäden über die Compliance fließen vielfältige Beobachtungen ein, deren Aussagekraft noch unklar ist. Bei 104 Patienten zwischen neun und 16 Jahren wurden multiple Compliancekriterien aus Behandlungsunterlagen, Behandler- und Patientenbefragung und Mundhygieneindizes erhoben. Bei einem Teil der Patienten wurden außerdem der psychologische Farbtest nachLüscher durchgeführt und die Tragedauer der Geräte objektiv gemessen. Zwischen den einzelnen Compliancekriterien bestaht werig Konsistenz. Termineinhaltung, Gerätepflege und Mundhygiene des Patienten gestatten im allgemeimm I eine Rückschlüsse auf sein Trageverhalten. Auch die klinische Einschätzung spiegelt nur längertestig. Compliancekriterienster des Patienten korrekt wider. Die Kombination klinischer Informationen mit psychological therapedea verspricht dagegen eine verbesserte Einschätzung des Trageverhaltens.
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  • 2
    ISSN: 1432-1106
    Keywords: Vestibular ; Posture ; Head stabilization ; Somatosensory ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The relative contribution of vestibular and somatosensory information to triggering postural responses to external body displacements may depend on the task and on the availability of sensory information in each system. To separate the contribution of vestibular and neck mechanisms to the stabilization of upright stance from that of lower body somatosensory mechanisms, responses to displacements of the head alone were compared with responses to displacements of the head and body, in both healthy subjects and in patients with profound bilateral vestibular loss. Head displacements were induced by translating two 1-kg weights suspended on either side of the head at the level of the mastoid bone, and body displacements were induced translating the support surface. Head displacements resulted in maximum forward and backward head accelerations similar to those resulting from body displacements, but were not accompanied by significant center of body mass, ankle, knee, or hip motions. We tested the effect of disrupting somatosensory information from the legs on postural responses to head or body displacements by sway-referencing the support surface. The subjects' eyes were closed during all testing to eliminate the effects of vision. Results showed that head displacements alone can trigger medium latency (48–84 ms) responses in the same leg and trunk muscles as body displacements. Nevertheless, it is unlikely that vestibular signals alone normally trigger directionally specific postural responses to support surface translations in standing humans because: (1) initial head accelerations resulting from body and head displacements were in opposite directions, but were associated with activation of the same leg and trunk postural muscles; (2) muscle responses to displacements of the head alone were only one third of the amplitude of responses to body displacements with equivalent maximum head accelerations; and (3) patients with profound bilateral vestibular loss showed patterns and latencies of leg and trunk muscle responses to body displacements similar to those of healthy subjects. Altering somatosensory information, by sway-referencing the support surface, increased the amplitude of ankle muscle activation to head displacements and reduced the amplitude of ankle muscle activation to body displacements, suggesting context-specific reweighting of vestibular and somatosensory inputs for posture. In contrast to responses to body displacements, responses to direct head displacements appear to depend upon a vestibulospinal trigger, since trunk and leg muscle responses to head displacements were absent in patients who had lost vestibular function as adults. Patients who lost vestibular function as infants, however, had near normal trunk and leg response to head displacements, suggesting a substitution of upper trunk and neck somatosensory inputs for missing vestibular inputs during development.
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  • 3
    ISSN: 1432-1106
    Keywords: Monosynaptic reflex ; Quadriceps ; Ia afferents ; Presynaptic inhibition ; Gait
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Amplitude modulation of the quadriceps H reflex was investigated during the early part of the stance phase of gait in normal human subjects. Stability of the M wave was used to ensure constancy of the effective stimulus strength. In all subjects there was a progressive decrease in the reflex amplitude throughout the early knee flexion (yield of the knee), whereas the quadriceps EMG activity remained constant or even increased. At an equal stimulus strength and EMG level, the reflex was often larger at the onset of the stance phase of gait than during voluntary contraction, whereas it was always smaller during the knee extension following the yield of the knee. It is argued that changes in presynaptic inhibition of quadriceps Ia terminals could account for this amplitude modulation of the monosynaptic reflex during gait. The possible role of changes in the gain of the quadriceps stretch reflex during bipedal gait is discussed.
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  • 4
    ISSN: 1432-1106
    Keywords: Tendon reflex ; Quadriceps ; Presynaptic inhibition ; Gait ; Ia afferents ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Amplitude modulation of the quadriceps tendon jerk reflex was investigated during the step cycle in normal human subjects. Reflex amplitude was compared with that obtained during a control stance condition, with “equivalent” levels of EMG activity and limb position. During gait there was a progressive decrease in the reflex amplitude early in the stance phase, i.e. during yielding of the knee, and it remained reduced throughout the step cycle. This pattern of changes in reflex amplitude correlated with neither the quadriceps EMG activity nor with the knee joint movements. The behavior of the tendon reflex was similar to that described for the modulation of the quadriceps H-reflex during the early stages of the stance phase of gait. In the latter study it was argued that changes in presynaptic inhibition of quadriceps la terminals could account for the amplitude modulation. We conclude that there is no dramatic change in the gamma drive to quadriceps muscle spindles: tendon reflexes are modulated during the step cycle in much the same way as H-reflexes, in spite of the peripheral and central differences between them. Similar behavior has been described for the soleus H-reflex and Achilles tendon reflex during gait although the modulation of these reflexes followed a different pattern than that seen in the quadriceps.
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  • 5
    ISSN: 1432-1106
    Keywords: Human gait ; Sural nerve ; Soleus ; Gas trocnemius ; Cutaneous reflexes ; Differential recruitment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Phase-dependent reflex modulation was studied by recording the electromyographic (EMG) responses in soleus (SOL) and gastrocnemius medialis (GM) to a 20 ms train of 5 electrical pulses, applied to the sural or tibial nerve at the ankle, in 14 volunteers walking or running on a treadmill. Although both the spontaneous activity and the reflex responses were usually similar for both muscles, instances were identified in which separate control was evident. During walking (4 km/h), activity in SOL started earlier in the stance phase than GM activity. Correspondingly, the amplitude of the reflex responses was larger in SOL than in GM in early stance, both ipsi- and contralateral to the side of stimulation. In some cases, the same stimulus could elicit contralaterally a suppression of GM in synchrony with a facilitation of SOL. These crossed extensor reflexes had a low threshold (1.2 × T) and a latency ranging from 72 to 105 ms. During running (8 km/h or more), responses were seen selectively in GM instead, without concomitant responses in SOL. Such responses had a latency ranging from 82 to 158 ms and they appeared during the first extension phase, at the end of the swing phase. In addition, selective GM responses, with latencies above 200 ms, were seen near the transition from stance to swing during running. These instances of separate reflex control of SOL and GM were correlated with step cycle periods during which the motoneurones of either one of these muscles received more spontaneous activation than the other. Nevertheless, it is argued that premotoneuronal gating must also be involved since the increased amplitude of the crossed SOL responses (in early stance) and of GM responses (at end swing) was not strictly linked to an elevated amount of spontaneous activity during these parts of the step cycle as compared to other parts.
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  • 6
    ISSN: 1432-1106
    Keywords: Stance regulation ; Compensatory EMG responses ; Rotational/translational perturbations ; Load receptors ; Postural reflexes ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary According to recent observations, influence of body load has to be taken into account for the neuronal control of upright stance in addition to the systems known to be involved in this regulation (e.g. afferent input from vestibular canals, visual and muscle stretch receptors). The modulation of compensatory leg muscle electromyographic (EMG) responses observed during horizontal body posture indicates the existence of a receptor system which responds to loading of the body against the supporting platform. This receptor should be located within the extensor muscles because a compensatory EMG response and a loading effect on this response was only present following translational, but not rotational impulses. As the EMG responses were identical to those obtained during upright stance, it is argued that these load receptors activate postural reflexes. According to recent observations in the spinal cat, this afferent input probably arises from Golgi tendon organs and represents a newly discovered function of these receptors in the regulation of stance and gait.
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  • 7
    ISSN: 1432-1106
    Keywords: Stance regulation ; Adaptational processes ; Developmental aspects ; Load receptors ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Recordings of electromyographic (EMG) leg muscle activity, head and joint movements and platform torque were taken in healthy subjects within three age groups (approximately 6, 10 and 〉22 years) standing upright upon a sinusoidally moving treadmill. The sinusoidal frequency was randomly changed between 0.5, 0.33 and 0.25 Hz, while the amplitude of the deflection was constant (±12 cm). During an adapted sinus, forward inclination of the body at the posterior turning point was associated with a slowly increasing tibialis anterior and decreasing gastrocnemius activity, while straightening of the body at the anterior turning point was associated with a sharply increasing gastrocnemius and decreasing tibialis anterior activity. The angle of forward inclination was greatest in the groups of children and was dependent upon both the sinus frequency and the child's height. The presumed programmed adjustment of the body inclination was such that the net effect of both inertial and gravitational forces acting on the body coincided approximately with the axis of the body at the posterior turning point. Changes of sinusoidal frequency were followed by compensatory responses, the amplitude of which depended upon the velocity of the body's displacement and the height of the subjects. In all three subject groups the response latencies were significantly shorter at the posterior turning point for the gastrocnemius response to a change from 0.5 to 0.25 Hz (105 ms for children and 119 ms for adults) than for the tibialis anterior response to a change from 0.25 to 0.5 Hz for which the values were 162 and 169 ms, respectively. This difference could be attributed to the forward inclination of the body at the posterior turning point which requires an earlier onset of compensatory extensor activity in order to maintain equilibrium. Adaptation to a new sinusoidal frequency occurred within 4 cycles following a change in sinus frequency. The phase shifts between treadmill position and the biomechanical and EMG signals that occurred during the adaptational process suggest that the position of the body's centre of gravity is the variable controlled by the programmed leg muscle activation. In young children the phase shifts during adaptation were absent, which may contribute to their greater instability. It is concluded that posture is continually adjusted in such a way that the resulting torque acting on the body during the treadmill movement becomes minimized. For this regulation load receptors in addition to the classical afferent impulses from visual, vestibular and muscle stretch receptors could play a major role.
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  • 8
    ISSN: 1432-1106
    Keywords: Tibial nerve ; Sural nerve ; Reflex modulation ; Reflex reversal ; Flexor reflex ; Human gait
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Phase-dependent reflex modulation was studied by recording the electromyographic (EMG) responses in ankle flexors (Tibialis Anterior, TA) and extensors (Gastrocnemius Medialis, GM and Soleus, SOL) to a 20 ms train of electrical pulses, applied to the tibial or sural nerve at the ankle, in human volunteers walking on a treadmill at 4 km/h. For low intensity stimuli (i.e. 1.6 times perception threshold), given during the swing phase, the most common response was a suppression of the TA activity with a latency of 67 to 118 ms. With high intensity of stimulation (i.e. 2.8 × T), a facilitatory response appeared in TA with a latency of 74 ms. This latter response was largest during the middle of the swing phase, when it was correlated with exaggerated ankle dorsiflexion. The TA reflex amplitude was not a simple function of the level of spontaneous ongoing activity. During stance, TA responses were small or absent and accompanied by a suppression of the GM activity with a latency ranging from 62 to 101 ms. A few subjects showed an early facilitatory, instead of a suppressive, GM response (88 to 136 ms latency). They showed a phase-dependent reflex reversal from a dominant TA response during swing to a facilitatory GM response with an equivalent latency during stance. The GM facilitation occurred exclusively during the early stance phase and habituated more than the TA responses. It is concluded that phase-dependent gating of reflexes occurs in ankle muscles of man, but only when vigorous extensor reflexes are present. More commonly, a phase-dependent modulation is seen, both of facilitatory and suppressive responses.
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  • 9
    ISSN: 1432-1106
    Keywords: Human gait ; Sural nerve ; Ankle angle ; Reflex reversal ; Phase-dependent modulation ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To investigate whether phase-dependent reversals in reflex responses on electromyography (EMG) are accompanied by movement reversals, a series of human volunteers were studied for their behavioural responses to sural nerve stimulation during running or walking on a treadmill. Low-intensity stimulation (〈 2.5 x perception threshold, T) of the sural nerve yielded facilitatory responses in the tibialis anterior muscle (TA), correlated with an induced ankle dorsiflexion (mean maximum 4°) in early swing. The same stimuli yielded primarily TA suppression and weak ankle plantar flexion (mean maximum 1°) at end swing. The correlated induced knee angle changes did not precede the ankle changes, and they were relatively small. Mean maximum flexion in early swing was 6.2°, while mean maximum extension was 3.7°. High-intensity stimulation of the sural nerve (〉 2.5 x T) always gave rise to suppression of the ongoing activity. This resulted in a second type of movement reversal. During late stance and early swing the responses in TA were suppressive (i.e. below background activity) and related to ankle plantar flexion. In contrast, the responses during early and middle stance consisted of suppression in extensor activity (gastrocnemius medialis and soleus) and ankle dorsiflexion. The data are discussed in terms of a new hypothesis, which states that the responses to electrical stimulation of cutaneous nerves during locomotion do not correspond directly to corrections for stumbling following mechanical perturbations during the step cycle. Instead, the data invite a reinterpretation in terms of the opening and closing of reflex pathways, presumably by a central pattern generator for locomotion.
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  • 10
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary To refine the genetic and physical mapping of the locus for Alport syndrome (ATS), 22 X-chromosome restriction fragment length polymorphism (RFLP) markers that fall between Xq21.3 and Xq25 were tested for genetic linkage with the disease and also mapped with respect to a series of physical breakpoints in this region. The location of the COL4A5 gene, which has recently been shown to be mutated in at least some families with Alport syndrome, was determined with respect to the same physical breakpoints. Two large Utah kindreds were included in the genetic studies, kindreds P and C, with 125 and 63 potentially informative meioses, respectively. Both kindreds have essentially identical nephritis; however, kindred P has sensorineural hearing loss associated with the nephritis, while kindred C does not. A mutation in COL4A5 has been demonstrated for kindred P, but no change in this gene has yet been detected for kindred C. Twelve informative probes did not recombine with the disease locus in either kindred (θ= 0.0, with combined lod scores for the two kindreds ranging from 7.7 to 30.0). The closest markers that could be demonstrated to flank the disease locus were the same for each kindred and thus the locations of the mutations causing the two disease phenotypes are not distinguishable at the current level of genetic resolution. The flanking markers are also useful for the resolution of questionable diagnoses and allow accurate estimates for these families of the rate of sporadic hematuria in noncarrier females (7%) and the penetrance of hematuria for carrier females (93%).
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