INFLUENCE OF LONG-TERM VIBRATION ON THE ACTIVITY OF THE SUPERIOR VESTIBULAR NUCLEUS NEURONS UNDER THE CONDITIONS OF STIMULATION OF THE HYPOTHALAMUS NUCLEI.

Prolonged vibration exposure leads to alterations of the central control mechanisms of both the vestibulo-ocular and the vestibulo-autonomic systems, including a change in the hypothalamic-vestibular relationships associated, in particular, with the supraoptic nucleus and paraventricular nucleus. Post-vibration disturbances of the vestibular function are largely due to adaptive changes in neurotransmitter activity. The dynamics of spike activity of single neurons of the superior vestibular nucleus (SVN) in response to high-frequency stimulation of the paraventricular and supraoptic hypothalamic nuclei after long-term vibration exposure were analyzed. Analysis of impulse activity revealed the prevalence of tetanic potentiation in the responses of SVN neurons to high-frequency stimulation of paraventricular and supraoptic nuclei of rats. Exposure of animals to vibration led to a decrease in the number of neurons with tetanic potentiations and significant dominance of post-tetanic potentiation. Morphological and histochemical results showed that under hypothalamic stimulation in the SVN neurons of rats exposed to vibration, there is an increase in metabolism and dephosphorylation processes in the cellular structures of the studied brain area, which ultimately provides optimal conditions for the processes of cell survival and regeneration.

The effects of vibration on the neuronal activity of lateral vestibular nuclei in unilaterally labyrinthectomized rats.

Unilateral labyrinthectomy causes distinct oculomotor and postural disorder syndromes that gradually deteriorate. Simultaneously, compensatory mechanisms for the suppression of pathological disorders were activated. The current study aimed to investigate the characteristics of impulse activity in the ipsilateral and contralateral neurons of the lateral vestibular nucleus of unilaterally labyrinthectomized rats during various periods of vibration exposure. A program analysis of the background impulse activity of the neurons in the right- and left-lateral vestibular nuclei of rats under normal condition and after right-sided labyrinthectomy was performed. The animals were subjected to different periods of vibration exposure 2 days after surgery (5-, 10-, and 15-day periods). A comparison of the characteristics of the background impulse activity of neurons in both nuclei of intact rats revealed an initial asymmetry in the values of the mean impulse frequency and coefficient of variation of interimpulse intervals. After 5 days of vibration exposure, the values of the mean impulse frequency of neurons in both Deiters' nuclei were almost equal in labyrinthectomized rats. The mean impulse frequency of neurons on the uninjured side was higher than that on the injured side on the days following vibration exposure. The characteristics and functional significance of the findings are discussed.

[THE EFFECTS OF THE STIMULATION OF HYPOTHALAMIC NUCLEI ON THE INFERIOR VESTIBULAR NUCLEUS AFTER LONG-TERM VIBRATION ACTION AND ADMINISTRATION OF PROLINE RICH PEPTIDE-1].

Vestibular dysfunctions after vibration action in a considerable degree by adaptive-adjustment changes of neurotransmitter processes are determined and regulation of which is possible by endogenous factors, particularly hypothalamic proline rich peptide-1. On Albino rats synaptic changes in single neurons of the inferior vestibular nucleus during high-frequency stimulation of hypothalamic supraoptic and paraventricular nuclei in condition of vibration action and systemic use of proline rich peptide-1 were studied. The poststimulus spike activity of inferior vestibular nucleus neurons in norm was manifested mainly in the form of tetanic potentiation and posttetanic potentation after vibration action. The combination of vibration action and proline rich peptide-1 restores the true balance of excitatory and inhibitory poststimulus reactions and increased level of survival the inferior vestibular nucleus neurons.

The effects of vibration on the baseline spike activity of neurons in the superior vestibular nucleus.

The characteristics of the baseline spike activity of neurons in the superior vestibular nucleus of rats were studied after exposure to vibration for five, 10, and 15 days using a computerized method for recording and analyzing interspike intervals. The distributions of neurons in terms of their regularity, their dynamic types, and the modalities of their interspike interval histograms were assessed. In intact animals, the mean spike frequency was 14.0 +/- 1.4 Hz. Changes in the main measures were seen at different durations of exposure to vibration, along with a significant increase in the mean neuron spike frequency. The results demonstrate changes in the level of the functional state of neurons in the superior vestibular nucleus after exposure to vibration. The characteristics and significance of the results are discussed.

Postvibration changes in the spike activity of neurons in the medial vestibular nucleus.

Changes in the baseline spike activity in the medial vestibular nucleus were studied after exposure to vibration for 5, 10, and 15 days. Studies addressed the distributions of neurons within this structure in terms of the regularity of their spike activity, the dynamics of neural flows, and the modalities of interspike histogram modalities. Mean values were calculated for the major statistical measures of baseline spike activity. Statistically significant changes in the major characteristics of neuron activity were seen in the medial vestibular nucleus at different periods of vibration exposure. Vibration was found to induce complex dynamic rearrangements in the baseline activity of neurons in this structure. The characteristics and functional significance of the results are discussed.

Responses of hypothalamic neurons to stimulation of the vestibular nerve and lateral vestibular nucleus in the rabbit.

Acute experiments were performed on rabbits to study the responses of neurons in the anterior, ventromedial, and posterior nuclei of the hypothalamus to single, paired, and rhythmic stimulation of the vestibular nerve and lateral vestibular nucleus of Deiters. The data obtained showed that neurons of the posterior nucleus of the hypothalamus were the most sensitive. Three types of response were seen from hypothalamic neurons, with short, long, and intermediate latent periods. This provides evidence that ascending afferent spike activity from the lateral vestibular nucleus of Deiters to the hypothalamus is mediated by mono-, oligo-, and polysynaptic pathways.

Age changes in the fatty acid composition of the lipids of certain actinomycetes.

The composition of the fatty acids of the total lipids and its changes during culturing of Act. fluorescens, Act. globisporus, Act. viridis, Act. roseoflavus var Act. roseofungini and two of its proactinomycetes-like variants, were studied. The qualitative composition of the fatty acids of all the strains studied did not differ; the assortment of acids contained 11 basic components: C14-C18 acids-saturated, with normal, iso, and anteiso structures, and monoenic of normal structure. As the mycelium grows, the age dynamics of the fatty acids in submerged culturing are characterized by an increase in the total of saturated branched acids and a decrease in the total number of unsaturated acids. In the case of surface culturing, this tendency is maintained for vegetative cells; when aerial mycelium appears, the sum of the two components mentioned is unchanged. The level of normal saturated acids is constant.