The study of the amnesia mechanisms is of both theoretical and practical importance. The mechanisms of anterograde amnesia are the least studied, due to the lack of an experimental model that allows ...studying this amnesia type molecular and cellular mechanisms. Previously, we found that conditional food aversion memory reconsolidation impairment in snails by NMDA glutamate receptor antagonists led to the amnesia induction, in the late stages of which (>10 days) repeated training did not cause long-term memory formation. In the same animals, long-term memory aversion to a new food type was formed. We characterized this amnesia as specific anterograde amnesia. In the present work we studied the role of epigenetic DNA methylation processes as well as protein and mRNA synthesis in the mechanisms of anterograde amnesia and memory recovery. DNMT methyltransferase inhibitors (iDNMT: zebularine, RG108 (N-Phthalyl-1-tryptophan), and 5-AZA (5-Aza-2'-deoxycytidine)) were used to alter DNA methylation. It was found that in amnesic animals the iDNMT administration before or after shortened repeated training led to the rapid long-term conditional food aversion formation (Ebbinghaus saving effect). This result suggests that amnestic animals retain a latent memory, which is the basis for accelerated memory formation during repeated training. Protein synthesis inhibitors administration (cycloheximide) before or immediately after repeated training or administration of RNA synthesis inhibitor (actinomycin D) after repeated training prevented memory formation under iDNMT action. The earlier protein synthesis inhibitor effect suggests that the proteins required for memory formation are translated from the pre-existing, translationally repressed mRNAs. Thus, we have shown for the first time that the anterograde amnesia key mechanism is DNMT-dependent suppression of the transcription of genes involved in memory mechanisms. Inhibition of DNMT during repeated training reversed these genes expression blockade, opening access to them by transcription factors synthesized during training from the pre-existing mRNAs.
•Memory reconsolidation impairment leads to anterograde amnesia development.•Retraining of amnestic grape snails did not induce long-term memory formation.•DNA methyltransferase inhibitor (iDNMT)+retraining induced memory formation.•The effect of iDNMT on memory formation depended on protein and RNA synthesis.•DNA methylation-dependent gene repression underlies the anterograde amnesia.
Hydrogen being an ecological fuel is very attractive now for engines designers. It is already actively used in rocket engines. There exist plans to use hydrogen in pulse detonation engines. However, ...peculiarities of hydrogen combustion kinetics, the presence of zones of inverse dependence of reaction rate on pressure, etc. prevent from wide use of hydrogen engines. Computer aided design of new effective and clean hydrogen engines needs mathematical tools for supercomputer modeling of hydrogen–oxygen components mixing and combustion gas dynamics.
The paper presents the results of developing verification and validation of mathematical model and numerical tool making it possible to simulate unsteady processes of ignition and combustion in engines of different types and to study its peculiarities. First, verification and validation of the chemical kinetic models for hydrogen oxidation were carried out through investigations on the ignition delay time on pressure, temperature, and equivalence ratio for hydrogen-oxygen mixtures. Then, the developed solver was used to model pre-mixed and non-premixed combustion and detonation related phenomena including deflagration to detonation transition.
•Behavior of ignition delay for hydrogen-oxygen mixtures was validated.•Detonation initiation, degeneration and reestablishing were simulated numerically.•Peculiarities of deflagration to detonation transition were resolved.
A methane line list for the HITEMP spectroscopic database, covering 0-13,400 cm−1 (>746 nm), is presented. To create this compilation, ab initio line lists of 12CH4 from Rey et al. ApJ, 847, 105 ...(provided at separate temperatures in the TheoReTS information system), are now combined with HITRAN2016 methane data to produce a single line list suitable for high-temperature line-by-line calculations up to 2000 K. An effective-temperature interpolation model was created in order to represent continuum-like features over the temperature range of study. This model is advantageous to previously used approaches that employ so-called "super-lines," which are suitable only at a given temperature and require separate line lists for different temperatures. The resultant HITEMP line list contains ∼32 million lines and is significantly more flexible than alternative line lists of methane, while accuracy required for astrophysical or combustion applications is retained. Comparisons against experimental observations of methane absorption at high temperatures have been used to demonstrate the accuracy of the new work. The line list includes both strong lines and quasi-continuum features and is provided in the common user-friendly HITRAN/HITEMP format, making it the most practical methane line list for radiative-transfer modeling at high-temperature conditions.
•Protein and RNA syntheses are necessary for amnesia induction.•The sensitivity of amnesia to retraining and reminders is reorganized over time.•Amnesia can be reactivated by a reminder ...presentation.•Late-stage amnesia that is resistant to retraining can be defined as specific anterograde amnesia.•The key characteristics of amnesia and memory formation are similar.
According to a common perspective, amnesia is a passive consequence of memory consolidation or reconsolidation impairment. The results of our own study, as well as literature data, allowed us to offer an interpretation of amnesia. Amnesia is an active process whose key characteristics are similar to those of other long-term plastic rearrangements of the brain, including learning processes. In accordance with this hypothesis, the review considers the data we obtained on the mechanisms of amnesia induction and development caused by impairment of conditioned food aversion memory consolidation or reconsolidation. In particular, experimental data indicating the dependence of amnesia induction on protein and RNA syntheses are described. After amnesia induction, a time-dependent reorganization of its processes is shown to occur. In early amnesia stages (< 10 days), a gradual decrease in the possibility of memory formation during a second training was observed. In late stages of amnesia (10 days or more), an unusual physiological phenomenon was revealed—the second training did not lead to the formation of long-term memory. This effect was specific, as memory for a new type of food could possibly be formed in these animals. The described properties of amnesia facilitate its characterization as specific anterograde amnesia. In addition, at an early but not late amnesia stages, reminder presentation caused amnesia reactivation, impairment of which by DNA methyltransferase inhibitors caused memory recovery. The results obtained allow us to characterize amnesia as a specific, time-dependent, separate process. In conclusion, the potential biological significance of the described type of amnesia is considered, and we discuss the possible molecular mechanisms underlying it.
The participation of DNA methylation and histone acetylation in the mechanisms of anterograde amnesia and memory recovery was studied on grape snails trained in conditioned food aversion. Anterograde ...amnesia developed 10 days after memory reconsolidation impairment with an NMDA glutamate receptor antagonist and was characterized by long-term memory formation impairment upon repeated training. DNA methyltransferase inhibitor injections to snails 1 h before repeated training, as well as 15 min or 4 h after repeated training, caused rapid formation of memory that persisted for at least 10 days. Injections of histone deacetylase inhibitor before repeated training also induced the formation of a stable long-term memory. However, administration of histone deacetylase inhibitor 15 min after repeated training initiated a temporary memory recovery. Injections of the inhibitor 4 h after repeated training were ineffective. These results indicate that histone-dependent chromatin remodeling and DNA methylation are selectively involved in the mechanisms of anterograde amnesia and memory recovery.
•The administration of cycloheximide/reminder causes amnesia in trained snails.•In amnestic snails, the re-exposure of cycloheximide/reminder causes memory retrieval.•Cycloheximide-induced amnesia ...was also reversed by an anisomycin/reminder application.
The involvement of protein synthesis in the mechanisms of conditioned food aversion memory impairment and recovery in grape snails was studied. It was found that protein synthesis inhibitor (cycloheximide) injections before a reminder by the conditioned stimulus (CS) caused amnesia development. Three days after amnesia induction, injections of cycloheximide or another protein synthesis inhibitor, anisomycin, combined with a reminder by four CSs resulted in memory retrieval, which was saved for 24 h. Cycloheximide injections and the administration of one CS as a reminder to an amnestic animals caused the memory expression only in response to this CS, while it was absent the next day. The isolated administration of a reminder or inhibitor injections without a reminder was not effective. It is suggested that amnesia is an active process and that one of its mechanisms may be a protein-dependent amnesia reactivation caused by a reminder. The administration of protein synthesis inhibitors led to impairment of amnesia reactivation and to recovery of the state formed before amnesia induction and thus to the recovery of conditioned food aversion memory.
The aim of the present study is to investigate problems of numerical simulations precision and stochastic errors accumulation in solving problems of detonation or deflagration combustion of gas ...mixtures in rocket engines. Computational models for parallel computing on supercomputers incorporating CPU and GPU units were tested and verified. Investigation of the influence of computational grid size on simulation precision and computational speed was performed. Investigation of accumulation of errors for simulations implying different strategies of computation were performed.
•Memory reconsolidation impairment induces amnesia, developing over time.•Injections of protein synthesis inhibitors + reminder led to memory recovery.•Recovered memory can persist for more than 10 ...days.•Assumed that the reminder induces protein synthesis-dependent amnesia reactivation.•Suggested that amnesia, including its reactivation, is an active process.
Memory recovery in amnestic animals is one of the most poorly studied processes. In this paper, we examine the role of protein synthesis and a reminder in the mechanisms of amnesia and memory recovery in grape snails trained to conditioned food aversion. Amnesia was induced by the impairment of memory reconsolidation using NMDA (N-methyl d-aspartate) glutamate receptor antagonists. In an early stage of amnesia (day 3), injections of protein synthesis inhibitors into animals combined with a reminder by a conditioned stimulus (CS) led to the recovery of aversive reactions to its presentation. Two types of changes in reactions to CS were revealed. In most animals, a persistent recovery of memory retrieval was found that lasted for at least 10 days. In other snails, aversive responses to CS persisted for 24 h. Isolated injections of inhibitors, injections of inhibitors and a reminder by the learning environment (without presenting a CS), usage of a differentiating stimulus instead of a CS, or inhibitor injections after the reminder did not affect the development of amnesia. The administration of protein synthesis inhibitors and a reminder in the late period after amnesia induction (10 days) did not affect its development or caused a short-term memory recovery. We suggest that amnesia is an active process that develops over time. The reminder induces the reactivation of the amnesia process dependent on protein synthesis, while the administration of protein synthesis inhibitors leads to the impairment of amnesia reactivation and recovery of the state formed before amnesia induction (i.e., recovery of conditioned food aversion memory).
•NMDA or serotonin receptor antagonists paired with reminder-induced amnesia.•At an early (1 and 3 days) amnesia phase, the retraining was facilitated.•In the late phase (10 and 30 days), ...NMDA-dependent amnesia was resistant to retraining.•In the late phase, 5-HT-dependent amnesia retraining caused memory formation.
Elucidation of amnesia mechanisms is one of the central problems in neuroscience with immense practical application. Previously, we found that conditioned food presentation combined with injection of a neurotransmitter receptor antagonist or protein synthesis inhibitor led to amnesia induction. In the present study, we investigated the time course and features of two amnesias: induced by impairment of memory reconsolidation using an NMDA glutamate receptor antagonist (MK-801) and a serotonin receptor antagonist (methiothepin, MET) on snails trained with food aversion conditioning. During the early period of amnesia (<10th day), the unpaired presentation of conditioned stimuli (CS) or unconditioned stimuli (US) in the same training context did not have an effect on both types of amnesia. Retraining an on 1st or 3rd day of amnesia induction facilitated memory formation, i.e. the number of CS + US pairings was lower than at initial training. On the 10th or 30th day after the MET/reminder, the number of CS + US pairings did not change between initial training and retraining. Retraining on the 10th or 30th day following the MK-801/reminder in the same or a new context of learning resulted in short, but not long-term, memory, and the number of CS + US pairings was higher than at the initial training. This type of amnesia was specific to the CS we used at initial training, since long-term memory for another kind of CS could be formed in the same snails. The attained results suggest that disruption of memory reconsolidation using antagonists of serotonin or NMDA glutamate receptors induced amnesias with different abilities to form long-term memory during the late period of development.
Computer aided design of new effective and clean hydrogen rocket engines needs mathematical tools for supercomputer modeling of hydrogen–oxygen components mixing and chemically reacting in rocket ...combustion chambers. The paper presents the results of computer code developing, verification and validation, making it possible to simulate unsteady processes of ignition and combustion of hydrogen fuel in rocket engines. Restrictions on unsteady gas dynamics working cycles supercomputer simulations due to accumulations of errors are developed.
•3-D code was developed modeling hydrogen combustion in engines on unstructured grid.•Hydrogen kinetic equations solver incorporating internal cycles was suggested to increase CFD precision.•Limitations for time steps number are introduced guaranteeing needed accuracy for CFD.•Results of simulations were verified comparing with other codes and validated in experiment.•Grid independent wall flux solver was developed and validated.
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