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Biomedical subjects

T A Mering

Publications and source records attributed to T A Mering.

At least 19 recordsLinked to original sources
PubMed2005

The effects of Mexidol on the acquisition of food-related conditioned reflexes and synaptic ultrastructure in field CA1 of the rat hippocampus after single acoustic stimuli with ultrasonic components.

The effects of a complex acoustic signal with ultrasonic components on the ultrastructure of synapses field CA1 of the rat hippocampus were studied in conditions of two-week courses of the wide-spectrum antioxidant Mexidol (compared with an untreated group); the effects of complex acoustic signals on the dynamics of acquisition of a food-related conditioned reflex using a standard stimulus (a tone) and on the acquisition of a trace conditioned reflex to estimating time intervals were also studied, in the same groups of rats. Controls consisted of unstressed rats treated and not treated with Mexidol. Ultrastructural analysis of the redistribution of vesicles in the synaptic terminals of hippocampal field CA1 showed that synaptic transmission was impaired when assessed one day after exposure to the complex acoustic signal. Mexidol prevented impairment of synaptic transmission. The complex acoustic signal had negative effects on conditioned reflex activity in rats and Mexidol had normalizing actions on the acquisition of conditioned reflexes in stressed rats. These results lead to the conclusion that the antioxidant Mexidol can be applied to the prophylaxis of the impairments in CNS cognitive functions frequently seen in stress.

Acoustic Stimulation↗
PubMed2003

The action of mexidol on the state of conditioned reflex activity after traumatic brain lesions.

It is demonstrated that even partial damage to the hippocampus is accompanied by impairments to counting time intervals lasting several months (1200-1500 presentations) without alteration of other complex conditioned reflex responses. After treatment with mexidol, which has a wide spectrum of actions, paticularly antioxidant. antihypoxic, and antistress, rats showed a normal process of acquisition of a conditioned reflex to time. Unlike animals of the control group, there was no prolonged period during which there was complete impairment of the mechanism for counting time intervals. Thanks to significant improvements in autonomic processes and emotional-motivational responses, experiments could use a large number of conditioned stimuli. For example, after brain trauma mexidol strengthened compensatory-restorative processes: animals showed accelerated recovery of impaired functions, with decreases in the rate of retrograde degeneration of brain areas directly connected to the damaged parts, phenomena such as Monakow diaschisis were not observed, and so on.

Algorithms↗
PubMed1976

[Use of focused ultrasound for local destruction of different brain structures].

It was demonstrated that destruction of the brain can be accomplished by different combinations of ultrasound intensity and duration of irradiation. By experimental means cavitational thresholds of brain tissues were determined and a calculation was made of increased temperature in the zone of focus in each separate regime of irradiation. The authors describe the foci of lesions where the main mechanism of destruction was only warmth, either only cavitation, either warmth and cavitation together. Irradiation of deep brain structures was not accompanied by changes of the cortical and subcortical structures, located above the focus of necrosis along the path of the ultrasound ray (light microscopy). The probability of a target hit into the given brain structure corresponded to the preciseness allowed in a stereotaxic operation.

Animals↗
PubMedDate not supplied

[Effect of mexidol on status of conditioned reflex activity after traumatic brain damage].

Even partial hippocampal lesions in rats resulted in a disturbance of time interval determination over the course of several months (1200-1500 presentations) other complex conditioned reactions being preserved. As distinct from the control animals, the long period of failure of time interval counting was absent in rats receiving Mexidol. Continuous time conditioning took place in these animals. Due to substantial improvement of autonomic processes and emotional reactions, it was possible to present a higher number of conditioned stimuli in experiments. Mexidol seems to improve the compensatory and recovery processes after brain injuries: the impaired functions recover faster, the rate of the retrograde degeneration in the lesioned brain structures decreases, phenomena like Monakov's diaschis are not observed etc.

Animals↗
PubMedDate not supplied

[The effect of removal of the frontal region of the brain on conditioned reflexes to time and available stimuli].

The experiments were made on six dogs by the motor alimentary technique. It has been shown that ablation of the frontal lobe (fields: F1; F2; F3; F4) does not eliminate previously elaborated conditioned reflexes to time, temporal differentiations and reversals. They were disturbed because of motor perseverance only during the first one to three months. A conditioned reflex to time and temporal differentiations are elaborated much slower in dogs with a preliminary lobectomy, as compared with intact animals. A conclusion is drawn that the frontal lobe is not directly involved in counting the time macrointervals.

Animals↗
PubMedDate not supplied

[The effects of Mexidol on food conditioning and synaptic fine structure of hippocampal field CA1 in rats exposed to a single acoustic stimulation with ultrasonic components].

The effect of exposure of rats to a complex acoustic signal with ultrasonic components on line structure of synapses of the CA1 field of the hippocampus was studied during a course treatment (two weeks) with broad-spectrum antioxidant Mexidol. Under the same conditions, the time course of food conditioning by a conditioned tone stimulus and acquisition of trace conditioned reflex (time interval counting) were studied in the same rat group. Rats non-exposed to stress against the background of Mexidol and without Mexidol treatment served as control. Analysis of fine structure of the vesicle redistribution in CA1 synapses revealed a reduction of the efficacy of synaptic transmission a day after the exposure to the complex acoustic stimulus. We found a negative effect of the complex acoustic stimulus on conditioning by tone and acquisition of time-counting trace reflex by rats. This effect was shown to be normalized by the course Mexidol treatment. The results suggests the expediency of Mexidol application for prevention of cognitive disorders, which are frequent under stress-inducing conditions.

Acoustic Stimulation↗
PubMedDate not supplied

[Conditioned reflex activity in the aging process in white rats].

In Wistar rats, irrespectively of their age, conditioned reflexes to present stimuli are preserved and elaborated. Neither the mechanism of time intervals estimation is disturbed in aged and old rats (24-32 months). Long intervals between experiments (3-5 months) do not influence their state. Distinct changes are revealed of spatial-temporal differentiations in T-maze: significant worsening of their state is observed in 8-10 months age; in this age it is neither possible to elaborate them again. In simplified experimental conditions in the T-maze the old rats preserve the spatial orientation.

Acoustic Stimulation↗
PubMedDate not supplied

[Effect of ablation of the septum pellucidum on the marking of time intervals].

It is shown that preliminary ablation of the septum lucidum (the rat group II) leads to a considerable (up to 1000 presentations) and prolonged (up to one year) worsening of the elaboration of time intervals estimation, as compared to intact animals and does not significantly influence the conditioned reflexes to time stabilized before the operation (the rat group I). The great worsening of time intervals estimation is due to disturbance of the very mechanism of the reflex to time. Differences are discussed between the two groups of the operated rats. The septum ablation does not affect the state of conditioned reflexes to present stimuli. In the greater part of the postoperative rats a lowering of alimentary motivation is observed that may be secondarily accompanied by a disturbance of time intervals estimation.

Acoustic Stimulation↗