Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Human  (7)
  • 2000-2004
  • 1995-1999  (6)
  • 1980-1984  (1)
  • 1
    ISSN: 1432-1106
    Keywords: Split-belt locomotion ; Interlimb coordination ; Adaptation ; Motor learning ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Split-belt locomotion (i.e., walking with unequal leg speeds) requires a rapid adaptation of biome-chanical parameters and therefore of leg muscle electromyographic (EMG) activity. This adaptational process during the first strides of asymmetric gait as well as learning effects induced by repetition were studied in 11 healthy volunteers. Subjects were switched from slow (0.5 m/s) symmetric gait to split-belt locomotion with speeds of 0.5 m/s and 1.5 m/s, respectively. All subjects were observed to adapt in a similar way: (1) during the first trial, adaptation required about 12–15 strides. This was achieved by an increase in stride cycle duration, i.e., an increase in swing duration on the fast side and an increase in support duration on the slow side. (2) Adaptation of leg extensor and flexor EMG activity paralleled the changes of biomechanical parameters. During the first strides, muscle activity was enhanced with no increase in coactivity of antagonistic leg muscles. (3) A motor learning effect was seen when the same paradigm was repeated a few minutes later — interrupted by symmetric locomotion — as adaptation to the split-belt speeds was achieved within 1–3 strides. (4) This short-time learning effect did not occur in the “mirror” condition when the slow and fast sides were inverted. In this case adaptation again required 12–15 strides. A close link between central and proprioceptive mechanisms of interlimb coordination is suggested to underlie the adaptational processes during split-belt conditions. It can be assumed that, as in quadrupedal locomotion of the cat, human bipedal locomotion involves separate locomotor generators to provide the flexibility demanded. The present results suggest that side-specific proprioceptive information regarding the dynamics of the movement is necessary to adjust the centrally generated locomotor activity for both legs to the actual needs for controlled locomotion. Although the required pattern is quickly learned, this learning effect cannot be transferred to the contralateral side.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-1106
    Keywords: Key words Tendon reflexes ; Biceps femoris ; Gait ; Ia afferents ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  During gait it is generally accepted that there is a reduction in amplitude of H-reflexes as compared to standing. For short-latency stretch reflexes, however, it is less clear whether a similar reduction in reflex gain is present during locomotion. Stretches of constant amplitude are hard to produce under these circumstances and for this reason some previous studies on the biceps femoris (BF) have used ”reduced gait” in which the stimulated leg is stepping on the spot while the contralateral leg is walking on a treadmill. With this method it was possible to show that BF tendon jerk reflexes are larger at end swing and therefore are likely to contribute to the EMG burst normally occurring in that part of the step cycle when the BF is rapidly stretched. In the present study two questions were addressed: first, whether the reflex is different in size during gait compared to standing and, second, whether it is modulated in size during the gait cycle not only during reduced but also during normal gait. It was found that during both types of gait there was a general reflex depression with regard to the respective control values obtained during standing at similar EMG activity levels. In previous studies on soleus and quadriceps, discrepancies between EMG activity and reflex amplitude have been ascribed to changes in presynaptic inhibition of Ia terminals mediating the afferent volley of the reflex. Based on the data presented, this may also be true for the BF. In both normal and reduced gait the reflex was similarly modulated in size, showing a maximum at the end of swing. This similarity implies that reduced gait may be useful as an acceptable alternative for normal gait in studies on phase-dependent reflex modulation during locomotion.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1432-1106
    Keywords: Key words Vision ; Locomotion ; Optic Flow Adaptation ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The effect of an optic flow pattern on human locomotion was studied in subjects walking on a self-driven treadmill. During walking an optic flow pattern was presented, which gave subjects the illusion of walking in a tunnel. Visual stimulation was achieved by a closed-loop system in which optic flow and treadmill velocity were automatically adjusted to the intended walking velocity (WV). Subjects were instructed to keep their WV constant. The presented optic flow velocity was sinusoidally varied relative to the WV with a cycle period of 2 min. The independent variable was the relative optic flow (rOF), ranging from −1, i.e., forward flow of equal velocity as the WV, and 3, i.e., backward flow 3 times faster than WV. All subjects were affected by rOF in a similar way. The results showed, firstly, an increase in stride-cycle variability that suggests a larger instability of the walking pattern than in treadmill walking without optic flow; and, secondly, a significant modulating effect of rOF on the self-chosen WV. Backward flow resulted in a decrease, whereas forward flow induced an increase of WV. Within the analyzed range, a linear relationship was found between rOF and WV. Thirdly, WV-related modulations in stride length (SL) and stride frequency (SF) were different from normal walking: whereas in the latter a change in WV is characterized by a stable linear relationship between SL and SF (i.e., an approximately constant SL to SF ratio), optic flow-induced changes in WV are closely related to a modulation of SL (i.e., a change of SL-SF ratio). Fourthly, this effect of rOF diminished by about 45% over the entire walking distance of 800 m. The results suggest that the adjustment of WV is the result of a summation of visual and leg-proprioceptive velocity informations. Visual information about ego-motion leads to an unintentional modulation of WV by affecting specifically the relationship between SL and SF. It is hypothesized that the space-related parameter (SL) is influenced by visually perceived motion information, whereas the temporal parameter (SF) remains stable. The adaptation over the entire walking distance suggests that a shift from visual to leg-proprioceptive control takes place.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1432-1106
    Keywords: Prehension ; Motor control ; Altered hand position ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Past studies have examined the coupling of reach and grasp components during prehensile movements. Many of these studies have supported the view that these components reflect the output of two parallel, though temporally coupled, motor programs. When the grip aperture is Altered prior to the onset of prehension from its usual, normally flexed position to one of maximal finger extension, our previous work has shown that the grasp component appears to reorganize itself during the reach. This reorganization, consisting of a brief closing and reopening of the grip aperture, only slightly influenced the temporal components of the wrist transport. The present experiment continues this research theme by examining the characteristics of grip aperture reorganization through the comparison of the kinematics of prehension components during movements to two different size objects under normal and Altered grip aperture conditions. It was hypothesized that if the grip reorganization is task dependent it should be related to object size. The experiment found that in the Altered grip condition reorganization did occur, as indicated by a slight closing and reopening of the aperture without influencing the transport of the wrist. The amplitude of and the time to the observed inflection point in the aperture time course were related to object size. The velocity of grip closing for the large object showed double peaks, with the first substantially smaller than the second. Moreover, for the small object, the velocity of grip aperture closing also was double peaked, but the difference between peaks was less pronounced. These changes in grip velocity suggest that the grip reorganization is related to object size. No effect of Altered aperture was observed on the transport component. For both object sizes in the Altered condition, the final peak velocity of grip aperture was statistically significantly correlated with transport time and time to peak deceleration. In contrast, such correlations were not observed for the initial peak velocity of the grip aperture. Furthermore, time to maximum grip aperture was correlated with both time to peak wrist velocity and time peak to wrist deceleration. Thus, as the reach progressed toward the object, the grip and transport components became more interdependent. The results are consistent with the notion that, when a well-practiced, coordinated act such as prehension is confronted with an Altered grip posture at the onset of the reach, the grip can be reorganized during the transport to preserve the relative timing between them. Thus these data add to the growing awareness that not only is there temporal coupling between the reach and grasp components but that these components may be integrated by higher-order control mechanism.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1433-8491
    Keywords: Haemodialysis ; Depression/etiology ; Affective disturbances/etiology ; MMPI/comparative study ; Human ; Hämodialyse ; Depression/Ätiologie ; Stimmungsschwan ; kungen/Ätiologie ; MMPI/vergleichende Studie ; Mensch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung 32 ambulante Hämodialyse-Patienten wurden über einen Zeitraum von 8 Tagen mehrfach täglich durch psychometrische Fremd- und Selbstbeurteilungsskalen in ihrer Befindlichkeit eingeschätzt. Ziel der Untersuchung war es, depressive Verstimmungen in ihrer Häufigkeit und Ausprägung bei Hämodialyse-Patienten zu erfassen. Es sollte zudem geprüft werden, inwieweit derartige depressive Verstimmungen zur Frage der biochemischen Determiniertheit von depressiven Syndromen beitragen können. Es fanden sich subjektiv erlebte kurzfristige depressive Stimmungsschwankungen in etwa 15% der Fälle, die in den psychometrischen Fremdbeurteilungen jedoch nicht zu objektivieren waren. Derartige depressive Verstimmungen sind somit als „Modelldepression“ für die biologische Depressions-Forschung nicht geeignet. Geringe Häufigkeit und Schwere der depressiven Verstimmungen, sowie psychopathologischer Längs- und Querschnitts-befund lassen die Hämofiltration als wesentlichen Depressionsfaktor im Sinne der Katecholamin-/Indolamin-Mangel-Hypothese unwahrscheinlich erscheinen.
    Notes: Summary Over a period of 8 days, 32 haemodialysis out-patients were studied. Psychometric alien- and self-rating questionnaires were completed twice a day. The aim of the study was to produce a survey of the frequency and severity of depression in haemodialysis patients. It was speculated that the potency of haemodialysis in producing depression might be a helpful model in searching for biochemical factors in this disorder. Self-ratings showed short-term depressive changes in mood in about 15% of cases, which were not confirmed by alien-rating scales. It is concluded that neither incidence and severity nor longitudinal and cross-sectional profiles support a biochemical determination of depression in haemodialysis patients.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-1432
    Keywords: Zinc-finger protein ; Human ; Mouse ; Chromosome location ; Divergent evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated the human homologue of Mok2 gene encoding a Kriippel-like protein. The identification of three cDNAs and genomic clones reveals that the human protein shows substantial structural differences with the mouse MOK2 protein. The mouse MOK2 protein is composed of seven tandem zinc-finger motifs with five additional amino acids at the COOH-terminal. This structural feature is also present at the end of the human MOK2 protein. The seven zinc-finger motifs show 94% identity between the two proteins. In addition, the human protein contains three additional zinc-finger motifs in tandem with the others and a nonfinger acidic domain of 173 amino acids at the NH2-terminal. The Southern analysis indicates that a single copy of these two genes is present in the genome. The human gene has been localized on chromosome 19 on band q13.2–q13.3. The comparison of human and mouse cDNA sequences reveals a strong identity in the sequences localized outside the seven highly conserved zinc-finger motifs. The divergence from their common ancestor results in the loss of a potential transcription activator domain in mouse MOK2 protein.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1432-0878
    Keywords: Key words: Interleukin-6 ; Interleukin-1β ; Tenidap ; Astrocytes ; Alzheimer’s disease ; Therapy ; Cell culture ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Tenidap is a structurally novel antirheumatic agent with anti-inflammatory and analgesic properties. Previous studies have shown that tenidap is able to inhibit the production and action of cytokines such as interleukin-1, interleukin-6 (IL-6) and tumour necrosis factor α. However, the mechanisms by which tenidap inhibits cytokine synthesis are not yet known. We investigated in the human astrocytoma cell line U373 whether tenidap inhibits IL-6 synthesis by inhibition of certain signal transduction processes leading to IL-6 synthesis. Cells were stimulated with different substances which have previously been shown to activate protein kinase A or C, reactive oxygen intermediates as well as transcription factors such as nuclear factor kappa B and AP-1 and which all result in IL-6 synthesis. Tenidap was a very potent inhibitor of IL-6 synthesis independent of the stimuli used, suggesting an inhibitory mechanism other than inhibition of a certain signal transduction pathway. Since IL-6 has been shown to be involved in the etiopathology of Alzheimer’s disease and since the use of nonsteroidal anti-inflammatory drugs appears to be of therapeutical benefit, it is concluded that tenidap should be tested in clinical trials in order to determine whether it may be useful for the treatment of Alzheimer’s disease.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...