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Biomedical subjects

R Rokyta

Publications and source records attributed to R Rokyta.

At least 73 records · Page 4Linked to original sources
PubMed1989

[Experimental injuries of the spinal cord].

The authors present the results of five years' research concerned with experimental injuries of the spinal cord. The authors studied in cats and rabbits four types of problems: 1. the dynamics of injuries of the spinal cord from the morphological and biochemical aspect, in particular the development and shape of the lesion after complete severing of the spinal cord at the L2 level which was performed by 10-second extradural compression of the spinal cord with an artery forceps. 2. The possibility of resection of the destroyed spinal tissue one week after the insult and the development of autodestructive processes after this resection. 3. Resection of the entire vertebra L2 in healthy animals and shortening of the spine by means of an original stabilization apparatus. 4. Resection of the vertebra, resection of the autodestroyed parts of the spinal cord and approximation of the stumps of the spinal cord by shortening the spine. The assembled findings are discussed in conjunction with contemporary research into the reconstruction of spinal functions and possible transplantations of the CNS.

Animals↗
PubMed1988

Experimental spinal cord injury: lumbar vertebra resection to shorten the gap between spinal cord stumps.

Experimental spinal cord transection injuries followed by spinal cord destruction and gentle resection of the destructed cord tissue necessarily lead to a gap between both of the cord stumps. For any attempts to reconstruct the cord or to bridge this gap by transplantation it may be useful to narrow or close the gap. This can be done by vertebral resection. The technique of upper lumbar vertebra resection in cats and rabbits with and without spinal cord lesion is presented. The spine is shortened by approximately 20 mm by spondylectomy. This length exceeds the 10-14 mm long gap in the spinal cord which is created by a spinal cord crush injury using haemostatic forceps and the subsequent destruction zone resection which is performed seven days later. The upper lumbar vertebra is resected by the posterior approach and the spinal cord is sufficiently exposed to perform spinal cord reconstruction experiments.

Animals↗
PubMed1988

Influence of cinromide on metrazol--induced seizures during ontogenesis in rats.

The effects of cinromide on two types of metrazol-induced seizures were studied in 236 male rats aged 7, 12, 18, 25 and 90 days. Cinromide was administered intraperitoneally in a dose of 25 or 50 mg.kg-1 30 min before a subcutaneous injection of metrazol. Major, i.e. generalized tonic-clonic seizures could be elicited by metrazol in all age groups. Cinromide was efficient against this type of seizures at all developmental stages, but its action in 7- and especially in 12-day-old rat pups was less marked than in older animals. Minimal metrazol seizures (predominantly clonic) could be reliably elicited since the age of 18 days. Cinromide was also able to suppress this type of seizures, but in adult rats the dose of 75 mg.kg-1 had to be administered because even the 50 mg.kg-1 dose was not sufficient. Quantitative changes of the antimetrazol action of cinromide were demonstrated during maturation in rats.

Aging↗
PubMed1986

Functional significance of the serotoninergic influence on neuronal activity of the somatosensory cortex in 12-day-old kittens.

Monoamines, which participate in synaptic transmission as transmitters, also accomplish the modulation of neuronal activity. The role of serotonin (5-hydroxytryptamine--5-HT) was investigated in 8 to 14-day-old kittens by means of iontophoretic application onto neurones of the somatosensory cerebral cortex. The most typical response was the inhibition of neuronal activity. Another type of reaction was generated by inhibitory interneurones. After the microiontophoretic application of 5-HT, the tonic response of cortical neurones to the stimulation of the sciatic nerve changed into a phasic response. It is being suggested that the application of 5-HT to cortical neurones increases the excitability of inhibitory neurones. Hence, the serotoninergic regulation of neuronal activity in the somatosensory cortex may be operational from the 11th to the 12th day of postnatal life in cats.

Animals↗
PubMed1985

EEG changes induced by convulsants interfering with GABAergic inhibition in rats. I. Cortical recordings.

Electrocorticographic changes induced by 3 convulsant drugs interfering with the GABA system were studied in 73 adult rats. Aminooxyacetic acid first elicited changes (periods of theta waves) nearly constantly in occipital regions. Bicuculline induced not only occipital theta waves but also groups of spikes with the same frequency in frontal regions; there was no predominance of one of these regions. 3-Mercaptopropionic acid invariably elicited groups of spikes in the frontal region as the first sign of its action. As it progressed, this rhythmic activity became generalized so that differences among the 3 drugs disappeared. Paroxysmal activity induced by the 3 drugs studied was identical. It always started with rhythmic spikes which were gradually transformed into spike-and-wave rhythm. Differences among the 3 convulsants studied were found in the very first electrocorticographic changes. Long latency to the onset of action of 3-mercaptopropionic acid and especially of aminoocyacetic acid qualifies these drugs for studies of preparoxysmal changes.

3-Mercaptopropionic Acid↗
PubMed1982

Somatotopic organization of nucleus reticularis thalami in chronic awake cats and monkeys.

Responses of cells in the nucleus reticularis thalami (nRT) to peripheral stimulation were studied in chronic cats and monkeys. The activities were recorded through glass micropipettes. Natural stimulation as well as electric stimulation of implanted nerves were employed in 5 cats and 2 monkeys. In the nRT, 30% of the cells studies in the cat and 60% in the monkey were driven by non-noxious stimulations. A topical organization was demonstrated; however, it is not as precise as that shown for the ventrobasalis (VB) nucleus. The size of peripheral fields was larger than that of cells in the VB nucleus. The modalities of activation of these cells were similar to those of the different specific thalamic nuclei. The mean response latency to peripheral stimulation was longer and the fluctuation in the latency more important than those of the specific thalamic relay. The observations lend support to the hypothesis that most, if not all, of the nRT neurons are innervated by axon collaterals of the thalamocortical or corticothalamic bundles. Burst activities were not numerous in chronic cats (12%) and scarce in monkeys. These bursting neurons are mainly found in the perigeniculate area.

Afferent Pathways↗
PubMed1981

Electrocorticographic activity induced by gamma hydroxybutyrate in the rat during ontogenesis.

GHB at a dose of 200 mg . kg-1 i.p. elicited groups of slow waves with a frequency of 4--5 Hz in both frontal and occipital ECoG leads in adult rats. In 25- an 18-day-old rats similar slow wave activity became continuous and exhibited a clear-cut maximum in the frontal regions. In 15- and 12-day-old animals slow wave activity was also registered in the frontal region but it was organized into short groups of unstable frequency. No ECoG effects of GHB could be found in 9-day-old rats.

Aging↗
PubMed1980

The influence of 3-aminopropansulphonic acid (3-APS) on thalamic neurons.

The possible pathways conducting pain are still being discussed. One of the possible pathways may pass through the centrum medianum (CM). In the present study the activity of neurones of CM in cats was recorded using glass-micropipettes. 3-aminopropansulphonic acid (3-APS), which is a GABA analogue was administered intravenously in a dose of 0.1, 0.2, 0.5 and 1.0 mmol/kg. The depressive effect starts at the dose of 0.2 mmol/kg. The duration of the effect depends on the dose of 3-APS. Hence 3-APS has a very strong effect on other thalamic neurones so that it may be used for influencing their activity.

Action Potentials↗