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211.
Schweigart G Chien RD Mergner T 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2002,147(1):89-97
Vestibular functions are known to show some deterioration with age. Vestibular deterioration is often thought to be compensated
for by an increase in neck proprioceptive gain. We studied this presumed compensatory mechanism by measuring psychophysical
responses to vestibular (horizontal canal), neck and combined stimuli in 50 healthy human subjects as a function of age (range
15–76 years). After passive horizontal rotations of head and/or trunk (torso) in complete darkness (dominant frequencies 0.05,
0.1, and 0.4 Hz), subjects readjusted a visual target to its remembered prerotational location in space. (1) Vestibular-only stimulus (whole-body rotation); subjects' responses were shifted towards postrotatory body position, this only slightly at 0.4 Hz and
pronounced at 0.1 and 0.05 Hz. These errors reflect the known physiological drop of vestibular gain at low rotational frequency.
They exhibited a slight but significant increase with age. (2) Neck-only stimulus (trunk rotated, head stationary); the responses showed errors similar to those upon vestibular stimulation (with offset towards
postrotatory trunk position) and this again slightly more with increasing age. (3) Vestibular-neck stimulus combination during head rotation on stationary trunk; the errors were close to zero, independent of stimulus frequency and the subjects'
age. (4) Opposite stimulus combination (trunk rotated in the same direction as the head, but with double amplitude); the errors were clearly enhanced, essentially
reflecting the sum of those with vestibular-only and neck-only stimulation. Taken together, we find a parallel increase in
neck- and vestibular-related errors with age, in seeming contrast to previous studies. We explain our and the previous findings
by a vestibular-neck interaction model in which two different neck signals are involved. One neck signal is used, in combination
with the vestibular signal, for estimating trunk-in-space rotation. It is internally shaped to always match the vestibular
signal, so that these two signals cancel each other out when summed during head rotation on stationary trunk. Because of this
matching, perceived trunk stationariness during head rotation on the stationary trunk is independent of vestibular deterioration
(related to stimulus frequency, age, ototoxic medication, etc.). The other neck proprioceptive signal, coding head-on-trunk
rotation, is superimposed on the estimate of trunk-in-space rotation, thereby yielding a notion of head-in-space. This neck
signal remains essentially unchanged with vestibular deterioration. Generally, we hold that the transformation of the vestibular
signal from the head down to the trunk proceeds further to include the hip and the legs as well as the haptically perceived
body support surface; by this, subjects yield a notion of support kinematics in space. As a consequence, spatial orientation
is impaired by chronic vestibular deterioration only to the extent that the body support is moving in space, while it is unimpaired
(determined by proprioception alone) during body motion with respect to a stationary support.
Electronic Publication 相似文献
212.
Yoshimitsu Inoue Mikio Nakao Syozo Okudaira Hiroyuki Ueda Tsutomu Araki 《European journal of applied physiology》1995,70(1):6-12
Eight older (60–65 years) and six younger (20–25 years) men were exposed to a standard heat stress for 60 min in summer, autumn, winter, and spring. The test consisted of placing the lower legs and feet in a 42°C water bath while sitting in constant environmental conditions (30°C and 45% relative humidity). The increase of rectal temperature (T
re) was significantly greater (P < 0.05) in autumn, winter, and spring than in summer for the older group, but significantly greater only in winter than in summer for the younger group (P < 0.05). The T
re was greater for the older group in all seasons, but of significance only in autumn and spring (P < 0.01). There were no significant season-related differences for metabolic heat production (m) and mean skin temperature (
sk) during the heat test in the respective groups, although the m and
sk were lower for the older group in all seasons (P < 0.01). In the older group total body sweating rate (msw) divided by T
re (total msw/T
re) decreased from summer to winter (P < 0.02) and did not differ between winter and spring, whereas total msw/T
re in the younger group increased in spring after decreasing from autumn to winter (P < 0.03). The variations of the value, local sweating rate on the back and thigh divided by T
re (back msw/T
re and thigh msw/T
re), were similar to those of the total msw/T
re in each group, except for back msw/T
re in the younger group, which did not increase from winter to spring. The total msw/T
re, back msw/T
re and thigh msw/T
re were significantly less for the older group in summer, autumn and spring (P < 0.05). The range of seasonal variations was significantly less for the older group (P < 0.001). The results indicated that, compared with younger men in older men, the enhancement of sweating function toward summer occurred later and its reduction toward winter occurred earlier despite a smaller range of seasonal variation and that older men had a somewhat lesser capability to maintainT
re when challenged by heat stress in all seasons. 相似文献
213.
用银染色法、免疫组织化学及透射电镜技术,对36例人肺的神经内分泌细胞进行了形态学和免疫组织化学观察。提示NE细胞发生了废用性退化,其原因可能与出生前后人肺功能改变有关。 相似文献
214.
215.
216.
Schwenkreis P Liepert J Witscher K Fischer W Weiller C Malin JP Tegenthoff M 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2000,135(3):293-299
The aim of our study was to measure the effects of the glutamate antagonist riluzole on different parameters of motor excitability, using transcranial magnetic stimulation (TMS) during 7 days of riluzole administration, and to correlate these effects with riluzole plasma levels. Nine healthy volunteers received a dose of 100 mg riluzole from day 1 to 7 of the study period. Electrophysiological examinations were performed on day 1 before and 2 h, 5 h and 8 h after riluzole administration, on day 2, day 3 and day 5 before riluzole administration, and on day 8. Plasma samples were taken simultaneously. The excitability of the motor cortex, supraspinal and spinal motor pathways was tested by studying intracortical facilitation and inhibition, the cortical silent period and motor threshold after TMS, as well as the peripheral silent period and F-wave amplitudes after electrical peripheral nerve stimulation. We found a significant reduction of intracortical facilitation, which correlated significantly with riluzole plasma levels. To a lesser extent, intracortical inhibition was enhanced on day 1, motor threshold was increased on day 8 and F-wave amplitudes were reduced. These changes did not correlate with riluzole plasma levels. We conclude that the main effect of riluzole in vivo is a reduction of intracortical facilitation, which is closely related to the drug's level in the plasma. The most probable mechanism involves an effect on glutamatergic synaptic transmission. 相似文献
217.
R. M. Müri K. M. Rösler C. W. Hess 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1994,101(3):521-524
Memorised sequences of saccades are cortically controlled by the supplementary motor area (SMA), as shown in animal experiments and in humans with isolated SMA lesions. We applied transcranial magnetic stimulation (TMS) in eight healthy subjects executing memorised sequences of saccades. Sequences of three targets were presented. Then, upon a go-signal, the subjects had to execute the appropriate sequences. Ten to fifteen sequences were performed in each experiment, and the number of errors were counted. The number of errors increased significantly if TMS was given 80 ms before or 60 ms after the go-signal, with the stimulation coil overlying the SMA. There was no significant increase in errors if different stimulation intervals were chosen (160ms and 120ms before the go-signal; 100 ms, 140 ms or 240 ms after the go-signal), if the coil was positioned inappropriately (e.g. over the occipital cortex), or if the stimulator output was too low. We conclude that TMS can interfere specifically with the function of the SMA during a critical time interval close to the go-signal. 相似文献
218.
目的:探讨脱氢表雄酮(DHEA)对干扰素-γ(I NF-γ)刺激下的人脐静脉内皮细胞(HUVECs)CD40/CD40L表达的影响。方法:原代培养人脐静脉内皮细胞,给予I NF-γ刺激和不同浓度DHEA干预。采用流式细胞术检测CD40/CD40L在细胞表面的表达,通过反转录-聚合酶链反应(RT-PCR)检测CD40/CD40L mRNA的表达。结果:I NF-γ刺激HUVECs表达CD40/CD40L,DHEA下调I NF-γ诱导的HUVECs表面CD40/CD40L的表达,同时对I NF-γ刺激下的CD40/CD40L mRNA的表达有抑制作用,并且呈剂量依赖性。结论:DHEA能减轻I NF-γ刺激下的人脐静脉内皮细胞CD40/CD40L的表达。 相似文献
219.
Transcranial magnetic stimulation: new insights into representational cortical plasticity 总被引:15,自引:5,他引:15
Siebner HR Rothwell J 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2003,152(1):1-16
In the last decade, transcranial magnetic stimulation (TMS) has been used increasingly as a tool to explore the mechanisms
and consequences of cortical plasticity in the intact human cortex. Because the spatial accuracy of the technique is limited,
we refer to this as plasticity at a regional level. Currently, TMS is used to explore regional reorganization in three different
ways. First, it can map changes in the pattern of connectivity within and between different cortical areas or their spinal
projections. Important examples of this approach can be found in the work on motor cortex representations following a variety
of interventions such as immobilization, skill acquisition, or stroke. Second, TMS can be used to investigate the behavioural
relevance of these changes. By applying TMS in its "virtual lesion" mode, it is possible to interfere with cortical function
and ask whether plastic reorganization within a distinct cortical area improves function. Third, TMS can be used to promote
changes in cortical function. This is achieved by using repetitive TMS (rTMS) to induce short-term functional reorganization
in the human cortex. The magnitude and the direction of rTMS-induced plasticity depend on extrinsic factors (i.e. the variables
of stimulation such as intensity, frequency, and total number of stimuli) and intrinsic factors (i.e. the functional state
of the cortex targeted by rTMS). Since conditioning effects of rTMS are not limited to the stimulated cortex but give rise
to functional changes in interconnected cortical areas, rTMS is a suitable tool to investigate plasticity within a distributed
functional network. Indeed, the lasting effects of rTMS offer new possibilities to study dynamic aspects of the pathophysiology
of a variety of diseases and may have therapeutic potential in some neuropsychiatric disorders.
Electronic Publication 相似文献
220.
Detection of IgE-mediated respiratory sensitization in workers exposed to hexahydrophthalic anhydride 总被引:10,自引:0,他引:10