Biomedical subjects
Publications and source records attributed to V D Avelev.
Treadmill training of spinalized rats creates conditions for early appearance of rhythmic locomotor movements of the hind limbs. Recovery of the movements was paralleled by an appropriate structural organization of neurons in the anterior horns of the distal compartment of the spinal cord.
Acute and chronic experiments on lower spinal (T10-T12) cats were performed to investigate the effects of epidural stimulation of the dorsal surface of the spinal cord on the initiation of locomotor activity. A zone located at the border between segments L4 and L5 was identified, stimulation of which induces locomotor activity. The parameters of epidural stimulation of the spinal cord effective in activating the stepping movement generator were identified. Epidural stimulation leading to the initiation of movement activity was shown to depend on intracentral and peripheral mechanisms activating the segmental, intersegmental and propriospinal reflex systems of the spinal cord. A leading role was demonstrated for the propriospinal system of the dorsolateral funiculi in activating the generators of stepping movements in epidural stimulation of the spinal cord.
An area initiating locomotor activity under conditions of the spinal cord surface stimulation (SCS) was found at the upper border of the lumbar enlargement (L4-5 spinal segments). Parameters of the SCS for activation of the spinal stepping generator (SSG) were identified. Activation of the SSG under the SCS was shown to occur because of interaction of the spinal and peripheral mechanisms. Primary role in the SSG initiation during the SCS belongs to the propriospinal system of the dorsolateral funiculi.
Activation of forelimb flexor reflex afferents (FRA) exerted a facilitating effect upon the reciprocal 1a IPSP recorded in extensor motoneurones of lumbosacral segments. The latency of this spatial facilitation was 18-20 ms, duration up to 60 ms, the amplitude of the test disynaptic 1a IPSP being several times greater than in the control. Facilitation of the 1a IPSP occurs against the background of the IPSP evoked by descending interlimb impulses. Therefore the facilitation of synaptic transmission in the 1a inhibitory pathway to extensor motoneurones induced by the descending interlimb volleys, favours more pronounced reciprocal interrelations between flexor and extensor spinal motor centres.
The effect of low-intensity millimeter wave electromagnetic radiation (MWR) on regeneration of the rat sciatic nerve after transection and microsurgical reapproximation was examined. Rats were exposed to 54 GHz MWR at a power density of 4 mW/cm2. It was found that MWR treatment of the femoral skin in the area of suture accelerated the regeneration of nerve fibers. At the twentieth postoperative day, the MWR-treated animals had a 32% increase in the regeneration distance compared to the control animals. The conduction velocity showed a 26% increase in the MWR-treated animals.
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Low intensity millimeter-wave electromagnetic radiation of less than 10 mW cm-2 power intensity has a nonthermal effect on the body and it is widely used in medical practice for treatment of various diseases. Nevertheless, the effect of EMR on biological tissues is not understood. The skin and its sensory receptors are considered to be responsible for EMR reception, but this has yet to be confirmed. The present experiments were designed to study the effect of millimeter-wave electromagnetic radiation on the ampullae of Lorenzini in skates, which are very sensitive to weak electrical stimuli at low frequency. Reception of low-intensity millimeter-wave electromagnetic radiation at 37-55 GHz by the electroreceptors (ampullae of Lorenzini) in the skate has been shown. At a power intensity of 1-5 mW cm-2 irradiating the duct opening at 1-20 mm distance caused a transient increase in the firing rate of a single afferent unit. When the power intensity was increased inhibitory responses were also observed. Some receptors responded with a prolonged excitatory activity lasting up to 30 min to the irradiation of the duct opening. Direct irradiation of the sensory cells produced only an inhibition, probably due to a rise in temperature. It is proposed that millimeter-wave electromagnetic radiation generates a d.c. potential at the vicinity of duct opening which can be detected by the electroreceptors.
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Transcranial electrical stimulation of opioid brain structures was studied for its effect on the sciatic nerve of rat after transection and microsurgical restoration of the nerve. It was shown that electrical stimulation accelerated regeneration of sensory and motor fibres of the sciatic nerve. Participation of endogenous opioid peptides in the regeneration of peripheral nerves is discussed.
A high functional stability of the cat spinal cord motoneurons was shown in conditions of long-term orto- and antidromic activation with frequency corresponding to their natural rhythmicity. The depression of reflex discharges was shown to be related not to any postsynaptic depression or presynaptic inhibition but to a drop of probability of the transmitter release from the primary afferents' terminals. Analysis of signs of the habituation phenomenon revealed their similarity to the homosynaptic depression phenomenon and, consequently, their submittance to the same principles of experimental analysis and consideration.
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Interaction of PSPs elicited by stimulation of hindlimb and forelimb afferent nerves was studied in lumbar flexor motoneurons of anesthetized cats. Activation of forelimb afferents evoked EPSPs of considerable duration; no IPSPs were observed. Stimulation of hindlimb flexor afferents evoked EPSPs in the same motoneurons, their early component being of segmental origin and their late component--of spino-bulbo-spinal one. Interaction of afferent systems of fore--and hindlimbs caused a long-lasting depression of EPSPs. The depression of EPSPs was not followed by generation of IPSPs in motoneurons, Possible integrative levels of interlimb inhibitory coordination are discussed.
Interaction of segmental, propriospinal and spino-bulbo-spinal components of the lumbar flexor reflexes evoked by activation of the hind-and forelimb afferents with paired stimuli was studied in anesthetized cats. Coincidence in time of a reflex discharge evoked by stimulation of the forelimb afferent nerves with monosynaptic hindlimb flexor reflex causes considerable facilitation of the latter. The monosynaptic reflex increases for 40-50 ms. tthe polysynaptic flexor reflexes of segmental, propriospinal and spino-bulbo-spinal origin act upon each other in both a facilitatory and an inhibitory manner. Facilitation takes place only during the period of coincidence of the responses, inhibition when the responses are separated in time. Three types of inhibition with duration of 7-15, 40-150, 300-500 ms were observed. Possible neuronal mechanisms of interaction of the above-mentioned responses and their role in the inter limb interrelations are discussed
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The effects of electromagnetic irradiation (EMI) of wavelength 5.6 mm (frequency 53.57 GHz) and power density 4 mW/cm2 on the recovery of function in damaged rat sciatic nerve were studied; damage was produced by nerve section followed by microsuturing. Irradiation was applied to the skin of the thigh in the area of suturing. Total action potential (TAP) recording from the nerve was used to study the functional properties of regenerating nerve fibers five months after lesioning. These experiments demonstrated that EMI had a stimulatory effect on regenerative processes in the nerve, in terms of 25-30% increases in the rate of action potential conduction along nerve fibers, with increases in TAP amplitude.