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Hník P. Holas M. Krekule I. Kříž N. Mejsnar J. Smieško V. Ujec E. Vyskočil F. 《Pflügers Archiv : European journal of physiology》1976,362(1):85-94
Using liquid ion-exchanger semimicroelectrodes with a side pore, we measured changes of extracellular potassium concentration (Ke
+) in adult rabbit and cat gastrocnemius muscles and in venous effluent blood flowing from the cat gastrocnemius muscle during various bouts of activity induced by sciatic nerve stimulation.
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| 1. | Isometric tetanic contractions (at 50 Hz) of various durations caused transient accumulation of Ke + which was non-linearly related to the duration of muscle activity. The peak values of Ke + in response to muscle stimulation were analogous in rabbits and cats, attaining values, e.g. after a 20-s isometric tetanus, between 8–9 mEq/lK+ in both species. |
| 2. | Potassium concentration in venous effluent blood (K ven + ) was transiently increased after isometric tetani. Since blood flow was measured at the same time, it was possible to calculate the amount of K+ lost by the muscle after tetani of various durations. A 32 g gastrocnemius muscle of the cat, for example, loses 9.36±1.52 EqK+ after a 20-s isometric tetanus, which corresponds roughly to 0.5% of the total muscle potassium content. The loss of K+ in this muscle was 29.3 pEq K+/impulse/100 g fresh muscle tissue. |
| 3. | There was no evident difference between the amount of K+ released during isometric tetani, or tetanic contractions performed under isotonic conditions. Single twitches evoked by indirect stimulation at 1 Hz for several minutes also induced a small rise in K ven + . |
| 4. | If the loss of K+ from the muscle into the blood stream is transiently prevented by arterio-venous occlusion installed immediately before a 10-s isometric tetanus, most K+ is released subsequently when blood flow is renewed, if the occlusion lasts for 20–25 s. It is not until blood flow is occluded for 40–60 s that most K+ is apparently resorbed and only a minor portion is released and is to be found in the venous blood. |
| 5. | The transient accumulation of muscle extracellular potassium may locally affect nerve endings, skeletal and smooth muscle cells. |
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In order to prevent chance finding of the hidden target in the Morris water tank task, the rigid underwater platform is replaced with a collapsible platform, resting at the bottom of the pool. A computerized videosystem tracks the rat's movement across the pool and raises the platform when the animal has stayed in the target area for a predetermined time. Acquisition of the task with the collapsible platform proceeds at a similar rate as with the rigid platform when the criterion conditions are easy (target distance 15 cm, target time 2.5 s), but gradually deteriorates when the target time increases to 10.0 s. Successful solution of the modified task requires accurate localization of the target under open loop conditions and is thus well suited for investigation of the fine structure of the cognitive maps and of their changes induced by lesions or drugs. 相似文献
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Computer analysis of a picture in ophthalmology makes objective evaluation of the clinical finding possible. After analogue-digital transfer the pictures of the fundus on a black and white negative and coloured positive 24 x 36 mm were analyzed on a Pericolor 2000 E computer. We measured the area of the glaucoma excavation of the papilla of the optic nerve, calculated the C/D ratio, assessed changes in the picture of the fundus in exudative diabetic maculopathy on paired slides obtained after a one-year interval. We evaluated changes of fluorescein penetration during fluoroangiography in different diseases. 相似文献
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P. Zalud M. Indra V. Straka I. Krekule 《Medical & biological engineering & computing》1976,14(6):636-643
A discriminator for the real-time segregation of the unit activity of different neurons according to any combination of the following parameters of its waveform is described: (a) positive peak amplitude (separated into seven levels); (b) peak value of the negative spike wave (seven levels); (c) time interval (partitioned into 16 classes) between consecutive crossings of two preset levels; (d) the sequence of positive and negative parts of the spike. The discriminator, which implements several innovations, has shown good results in practical applications. The output of the discrimiminator (coded into 12 bits) can be evaluated either by a laboratory computer where it acts as a peripheral device, or by a supplementary apparatus, which is also described. 相似文献
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