Biomedical subjects
Publications and source records attributed to V I Arkhipov.
Single administration of kainic acid to Wistar rats impaired quenching of the conditioned response and increased the number of perseverative reactions 2 weeks postinjection. Indomethacin prevented behavioral disturbances induced by kainic acid.
The effects of the neurotoxin kainic acid on a food-producing habit were studied in Wistar rats in an experimental chamber. Single doses of kainic acid at a subconvulsive dose (8 mg/kg, i.p.) were found to impair the habit, onset of impairment being delayed by several weeks rather than immediate. Conversely, administration of the neurotoxin at the convulsive dose (10 mg/kg) impaired reproduction of the habit with onset within several hours after treatment and persistence for periods of up to 10 days, though this dose did not prevent the acquisition of a new food-procuring habit. These defects in the reproduction of long-term memory traces were explained in terms of the characteristics of the effects of kainic acid on the hippocampal system, which is the most susceptible to systemic administration of the neurotoxin.
The singlet-triplet splitting of geminate polaron pairs in a ladder-type conjugated polymer has been studied by the thermally stimulated luminescence technique. The energy gap separating the singlet and triplet states of the geminate pairs is measured to be in the range of 3-6 meV, depending on the polymer morphology. The results of correlated quantum-chemical calculations on a long ladder-type oligomer are fully consistent with the observed values of the geminate polaron pair singlet-triplet gap. Such low splitting values have important implications for the spin-dependent exciton formation in conjugated polymers.
Lipid composition of homogenate and neuronal and glial nuclei of the brain cortex of Wistar rats was studied under normal conditions and after seizures induced by injection of picrotoxin. Seizures increased contents of lysophosphatidylcholine, sphingomyelin, and total phospholipids in the homogenate. In neuronal nuclei contents of total phospholipids, sphingomyelin, phosphatidylcholine, and phosphatidylserine decreased, and contents of free fatty acids and lysophosphatidylcholine increased. In glial nuclei content of total phospholipids decreased and content of free fatty acids increased. The role of changes in the lipid composition of the neocortex cells during seizures and the involvement of lipid messengers in signal mechanisms are discussed.
Effect of the neurotoxin kainic acid to the food-procuring task were studied in Wistar rats. A single injection of the acid in subconvulsive dose (8 mg/kg) impaired the task performance within some weeks but not immediately after the treatment. Higher doses of kainic acid (10 mg/kg) impaired the task performance within a few hours after treatment for up to 10 days. The treatment did not prevent rat's learning of a new task in the same experimental chamber. The revealed deficit in the long-term memory retrieval might be explained by specific effects of kainic acid upon the hippocampal system.
In this paper, results are reported on the concentrations and activity ratios of 137Cs, 239+240Pu and 238Pu in soils, lichen and bottom sediments collected at the peaceful underground nuclear explosion sites "Craton-3" and "Crystal" (Republic of Sakha (Yakutia), North-East Siberia). At the "Craton-3" site, 239- 240Pu concentrations in the range 6.2 mBq/g to 5.9 Bq/g in surface soils (0-5 cm) and 239+240Pu concentrations up to 7.4 Bq/g in lichen were observed. The 137Cs concentration in measured soils range from 0.52 to 216 Bq/g for the near-plume and from 1.65 to 21.5 Bq/g for the far-plume. In lichen, 137Cs concentration varied from a global background level up to 251 Bq/g. Radioactive contamination at "Crystal" demonstrates an extremely irregular distribution of 239,240Pu and 137Cs in environmental samples taken at locations within 150 m radius of the site. Further work on compiling detailed maps of radioactive contamination of the territory around "Craton-3" and "Crystal" is discussed.
Wistar rats were trained food-procuring task for 5 days and then extinction of the operant behavior was studied for 6 days after injection of an epileptogen (kainic acid, 8 mg/kg, intraperitoneally). Kainic acid induced long-term impairment of inhibitory processes in the brain, which impeded extinction of a conditioned response. This effect was prevented by daily injections of anticonvulsant sodium valproate (300 mg/kg for 4 days).
The content of lipids in rat cortical tissue homogenate and fraction of neuronal nuclei was determined under normal conditions and after picrotoxin-induced seizures. Changes in lipid composition of homogenate and nuclear fraction differed considerably. In homogenate, the content of sphingomyelin, lysophosphatidylcholine, and total phospholipids increased, while the content of free fatty acid remained unchanged; in the nuclear fraction the total phospholipid content decreased, while the concentration of free fatty acids increased.
The phenomenon of dissociated memory retrieval is observed when some influences (for example, pharmacological) on the brain result in specific changes of long-term memory. The purpose of present paper is to reveal possibilities of the phenomenon for study of long-term memory retrieval. Pharmacologically-induced dissociated states could be identified when the retrieval of responses learned before treatment is temporarily blocked by the drug influence, but the ability of the animals to learn new tasks is intact. Furthermore, memory traces that were formed in drugged state are not accessible for the retrieval in normal state and only the same drug treatment allows retrieving them. In the present work, dissociated learning of food-motivated tasks was carried out in Wistar rats with cholinesterase inhibitor physostigmine (0.5 mg/kg, intraperitonealy) or general anaesthetic sodium pentobarbital (15 mg/kg, intraperitonealy.). The retrieval of dissociated responses was studied under the influence of various doses of the same drugs. The results revealed the asymmetry of memory dissociation with physostigmine in contrast to pentobarbital-induced memory dissociation. Gradual access for the retrieval of dissociated memory traces after pharmacological modulation of cholinergic and GABA-ergic brain systems was shown. It was suggested an important role of hippocampus in memory dissociation, as a structure-performing match-mismatch operations between different retrieved memory traces.
Explore the source record for details and available documents.
Picrotoxin administration decreased the incorporation of labelled phosphate in neurospecific protein synapsin I in vitro in cortex. In the animal hippocampus, the incorporation was more expressed. The data obtained suggest that activation of the cAMP-dependent phosphorylation occurs during seizure in the cortex.
In vitro protein phosphorylation of synaptic membranes isolated from neocortex and hippocampus of ground squirrels was studied. Three functional states of animals were investigated: torpid, awakened and active normothermic. Phosphorylation of a protein with a mol. wt of 53 kDa was independent on the functional state of the animals. Incorporation of 32P into this protein was greater in membranes of torpid and awakened squirrels than in membranes of active animals. These results suggest that protein phosphorylation is involved in the maintenance of membrane functions during hibernation.
In the present investigation the functional activity of transport systems mediating the GABA and L-glutamate uptake into nerve terminals of the rat brain cortex and hippocampus in response to a single carbacholine administration to hippocampus was studied. It has been established that synaptosomes isolated from the brain cortex and hippocampus of rats used in the experiments 24 h after a single carbacholine injection possess an increased capability of GABA and L-glutamate accumulation, and 48 h later the GABA and L-glutamate uptake begins to return to its control level and was equal to it on seventh day after injection.
Dissociated learning of rats in the normal state and the state of amnesia produced by pentobarbital (15 mg/kg, ip) was carried out. Rats were trained to approach a shelf where they received food reinforcement. In Group 1 the rats were trained under the influence of pentobarbital to run to the same shelf as in the normal state. In Group 2 the rats were trained to approach different shelves in different drug states. It was shown that memory dissociation occurred in both groups. Differences in the parameters of training under the influence of pentobarbital between Groups 1 and 2 were revealed. These findings show that the brain-dissociated state induced by pentobarbital is formed with the participation of the mechanisms of information perception.
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 stage of retrieving long-term memory traces is discussed; studies of this stage can be performed using the phenomenon of dissociated brain states. These states arise in response to various external influences and are accompanied by selective, reversible derangements of retrieval processes without alteration of the mechanisms involved in perceiving and fixing information. Analysis of the appearance of dissociated states induced by pharmacological treatments leads to several conclusion: a) reversible derangements affecting the retrieval function are typical of types of memory which depend on attention; b) the hippocampus plays a key role in selecting engrams for extraction from long-term memory; c) the brain's cholinergic and GABAergic mediator systems are involved in regulating the retrieval of long-term memory traces; d) stable derangements of the retrieval of long-term memory traces are accompanied by deep molecular-cellular changes in the hippocampus, including alterations in genetic elements and phosphorylation of synaptic proteins.