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Biomedical subjects

I Todorov

Publications and source records attributed to I Todorov.

At least 37 records · Page 2Linked to original sources
PubMed1991

Memory effects of a group of newly-synthesized pyrrolidine derivatives with putative nootropic effect.

The original pyrrolidine derivatives with putative nootropic effect: para-chloro-phenoxyacetyl-2-pyrrolidinone (Mf-P), 1-adamantanyl-2-pyrrolidinone (A-P), 2-oxo-1-pyrrolidine-3,7-dimethylxanthine (A-T) and para-benzoyl-1,4-dipyrrolidinone (p-P), were studied. Toxicological screening performed on mice demonstrated the low toxicity of the compounds. Five- or seven-day oral administration of the substances to rats in a dose of 100 mg/kg weight facilitated the learning process and improved the memory of the rats with most of the conditioned-reflex methods used. Application of Mf-P to 2- and 24-month-old rats for 8 days induced changes in the levels of some biogenic monoamines in the brain structures studied. The results obtained, as well as the results of other studies in this laboratory, show that the pyrrolidine derivatives studied, which can be considered to be original new aniracetam analogues, improve the memory process. This effect varies strongly depending on the regime of application of the compounds studied, on the memory capacity of the experimental animals and on the experimental method used. The changes in the brain neurotransmission induced by the substances studied play an essential role in their mechanism of action.

Animals↗
PubMed1988

U4 and U6 small nuclear ribonucleoprotein particles. 2. Evidence for their involvement in pre-mRNA splicing.

The in vitro splicing of pre-mRNA of the human beta-globin gene in the presence of HeLa cell nuclear extract was investigated. Splicing was inhibited by auto-antibodies against U4 and U6 snRNP particles. No intermediates or products of the splicing reaction were evident in the presence of antibodies against U4 and U6 snRNPs which suggests their involvement in pre-mRNA splicing.

Antibodies↗
PubMed1988

U4 and U6 small nuclear ribonucleoprotein particles. 1. Fractionation and characterization of snRNPs containing U4 and U6 RNAs.

The isolation of U4 and U6 small nuclear ribonucleoprotein particles (snRNP) was undertaken, since there has been no reliable method for their fractionation established. The procedure subjects a nuclear extract from HeLa cells to several types of ion exchange chromatography at moderate ionic strength, electrophoresis on agarose gels, transfer of the particles on DEAE cellulose paper, and elution with ammonium chloride. The purified U4 and U6 snRNPs contain U4 and U6 RNAs, respectively, and a set of six polypeptides, present in U4 RNPs and seven polypeptides in U6 snRNP particles. Five major proteins with molecular masses of 70, 64, 47, 40.5 and 24 kD are common to both assemblies. In addition U4 RNPs contain one polypeptide of 25.1 kD which is unique for this class of particles, while U6 RNPs possess two polypeptides with molecular masses of 31 and 18 kD which are not present in U1, U2 or U4 snRNPs. The U4 and U6 RNP particles thus fractionated retain their antigenicity as judged by their reaction with auto-antibodies from patients with lupus erythematosus.

Chromatography, Affinity↗
PubMed1986

Effects of meclofenoxate on learning and memory--dependence on the experimental conditions.

In experiments on male albino rats, it was found that meclofenoxate at a dose of 100 mg/kg i. p. applied 7 days before and 5 days during shuttle-box training did not influence learning but significantly facilitated retention (retention test was given 7 days after the end of training). With the step-through method for passive avoidance meclofenoxate at the same dose applied for 7 days improved learning and retention. In the staircase maze training with alimentary reinforcement and in the step-down passive avoidance situation, meclofenoxate at a single dose (50 mg/kg i. p.) applied before or immediately after training only tended to facilitate learning and retention, while applied at the same dose twice daily for 5 days, it significantly improved learning and retention. When meclofenoxate at a dose of 50 mg/kg i. p. was administered twice daily for 5 days in parallel with the staircase maze training, learning reached its maximum on the 5th day and remained at this level till the 10th training day even after withdrawal of meclofenoxate. In the control animals the improvement of learning progressively increased till the 10th training day. The present results suggest that the learning- and memory-facilitating effect of meclofenoxate is influenced by the training method, motivation, dose used and treatment duration.

Animals↗
PubMed1986

Effects of alcohol aqueous extract from Rhodiola rosea L. roots on learning and memory.

The effect of alcohol-aqueous extract (1:1) from Rhodiola rosea L. roots on the processes of learning and memory is studied on rats. Several methods of active avoidance with negative and positive reinforcements are used, as well as of passive avoidance. Using the maze-method with negative (punitive) reinforcement, it has been found that Rhodiola extract in a single dose of 0.10 ml per rat essentially improves learning and retention after 24 hours. Significant improvement of the long-term memory is also established in memory tests after 10-day treatment with the same dose of the extract. In the other two doses tested (0.02 and 1.0 ml per rat) the extract has no substantial effect on learning and memory. In a dose of 0.10 ml per rat the Rhodiola extract had a favourable effect on the training process using the "staircase" method with positive (food) reinforcement as well. With the other methods used (active avoidance method with negative reinforcement "shuttle-box" and passive avoidance methods "step down" and "step through") Rhodiola extract in the dose used (0.10 ml per rat) had no substantial effect on learning and memory (a certain deterioration of the training process was even observed using the "shuttle-box" method, while the "step-down" method resulted in deterioration of the memory). The great significance of the method used for studying the effects of the pharmacological agents on learning and memory for the results obtained is evident.

Administration, Oral↗