[Nucleotide level evaluation of the genetic variability of the human population in ecologically unfavorable regions of the Techa river].
Explore the source record for details and available documents.
Adolescent↗
Biomedical subjects
O A Timofeeva
Publications and source records attributed to O A Timofeeva.
Delayed development of spontaneous seizures and prolonged convulsive state in rats after massed stimulation of the anterior piriform cortex.
We studied the short- and long-term epileptogenic effects of massed stimulation (MS) of the piriform cortex. Sprague-Dawley rats with electrodes implanted bilaterally in the anterior piriform cortex and the dorsal and ventral hippocampi underwent MS: electrical stimulation of the left piriform cortex every 5 min for 6 h (afterdischarge threshold, 60 Hz, 1 ms, 1 s). Animals were retested (5 stimulations) 3-4 times later at different time points to check for the kindled state. Our data showed that MS resulted in delayed development of severe epilepsy. The interval between MS and the first appearance of convulsive response (2 weeks) was characterized by deep refractoriness to seizure (silent period). Unexpectedly, dramatic seizure activity occurred 4-7 weeks after MS. This was manifested by (1) generalized tonic-clonic convulsions with multiple failings, which were elicited repeatedly during retest; (2) frequent progression of elicited generalized convulsions into a prolonged (> 8 min) postictal convulsive state expressed mainly by continuous partial seizures and even new bouts of generalized seizures, and (3) development of mild spontaneous seizures. We found that epileptiform activity predominated in the ventral hippocampus. Mossy fiber sprouting was also most pronounced in this area. We propose that the MS resulted in formation of pathological circuits which involve both piriform cortex and ventral hippocampus and lead to severe epilepsy.
Aging↗
Bilateral hippocampal interictal spiking and kindling expression in rabbits.
The temporal/spatial dissemination of interictal spikes among different brain structures was studied during the course of kindling to determine if the long-term dissemination pattern reflects the rate and expression of kindling. The experiments were conducted on adult rabbits with chronically implanted electrodes (dorsal hippocampus, amygdala, caudate, all bilateral, sensory motor and occipital cortices). Rabbits (n = 13) were subjected to once daily electrical stimulation in the left hippocampus. Kindling resulted in the development of two different epileptic phenomena: 7 animals quickly (in 2-3 weeks) achieved a fully kindled state, characterized by generalized seizures, whereas the remaining 6 rabbits did not reliably progress beyond partial seizures even after more prolonged stimulation. Animals were accordingly divided into two groups referred to as generalized seizure and partial seizure. The temporal/spatial dissemination pattern, particularly in the two hippocampi, was very different between the groups. In both groups interictal spiking originated in one of the hippocampi independent of site stimulated and represented formation of the primary hippocampal epileptic focus. The generalized seizure group demonstrated stability of the primary hippocampal epileptic focus with permanent predominance of spiking in it over the course of kindling, and a high level of bilateral synchronous hippocampal interictal spiking. In the partial seizure group the primary hippocampal epileptic focus was established during the first 2-3 weeks of stimulation. This was later suppressed upon the development of an independent secondary focus in the opposite hippocampus. These animals also displayed very low levels of synchronous bilateral hippocampal interictal spiking. We suggest that an antagonistic relationship can develop between mirror hippocampal epileptic foci. This can be associated with a low level of bilateral hippocampal synchronous spiking, kindling retardation, and manifestation of partial seizures.
Analysis of Variance↗
Apparent disappearance of postseizure inhibitions and intensity of seizures during the development of rapid kindling in rabbits.
The evolution of seizures and postseizure inhibitions in the course of 'rapid kindling' and after the termination of stimulation were studied in rabbits with chronically implanted electrodes (neocortex, dorsal hippocampus, amygdala, caudate nucleus). The amygdala (n = 4) or hippocampus (n = 7) was electrically stimulated every 5 min. Generalized convulsions and wide-spread electrographic epileptic changes together with a striking shortening of postictal refractory periods were produced by this procedure within 2-6 h. In most cases, these epileptogenic effects continued their progression after the termination of stimulation for more than 2-4 weeks. The degree of reduction of postseizure inhibition durations was significantly greater than the degree of increase of generalized motor seizure durations. These may be mediated by mechanisms which facilitate the onset of seizure but do not significantly influence seizure expression.
Animals↗
[The central structural interrelations during kindling electrostimulations of the hippocampus].
The rate of kindling development was studied in rabbits with chronic electrodes (neocortex, hippocampus, amygdala, caudate nucleus) in respect to distribution of epileptic activity over the brain structures. The differences of individual kindling development depended on the distribution of interictal spikes over the brain structures and the degree of their subordination to the primary hippocampal focus. The kindling effects seem to develop rapidly in those cases when primary hippocampal epileptic focus plays a role of pathological determiner which subordinates and synchronizes the activity in other structures. When competitive inhibitory influences prevail in the interrelationships between primary and secondary hippocampal foci, neither pathological hippocampal determiner nor kindling effects occur.
Action Potentials↗
[Comparative characteristics of epileptic syndromes induced by kindling-electrostimulation of limbic structures with 24-28 hour and 5 minute intervals].
The experiments were conducted on rabbits with chronical electrode implants 2 weeks after the implantation. Animals were divided into 4 groups. It was established that in animals with rapid kindling the duration of motor seizures was longer, the generalization of spiking in the brain structures was significantly lesser. Postictal refractory period for these animal groups was inhibited to a marked degree. Our data showed that the inhibition of postictal refractory period and facilitation of motor seizures in the case of rapid kindling cannot be explained only by weakening of antiepileptic mechanisms.
Amygdala↗
[Kindling of the limbic structures with a shortened interstimulus interval].
We investigated the possibility to produce hippocampal or amygdala kindling syndrome in rabbits which had been electrically stimulated at a fixed interval between stimuli at 5 min. Animals were prepared with chronically implanted electrodes (neocortex, hippocampus, amygdala, nucleus caudatus). The initial stimuli produced only localized effect, but repeated applications of the stimuli progressively increased the seizure activity resulting in generalized kindled convulsions after 2-4 h period. At the first stage generalized seizures were followed by long lasting refractory period, but at the end of the procedure almost all stimuli evoke major motor seizures and recurrent widely spread electrographic epileptic changes. The most noteworthy findings emerging from this study is the inhibition of postictal seizure inhibition period. This effect was independent of whether stimulated the electrode was positioned in the hippocampus or amygdala, but the hippocampal formation occupied the central position for the once and propagation of the seizure activity in all cases. When established this syndrome persisted without any attenuation for some weeks. It was concluded that this model of rapid development of kindling syndrome is useful for investigation of the nature of epilepsy and postictal seizure inhibition.
Amygdala↗
[Significance of the hippocampus in the development of convulsive syndrome by kindling electrostimulation of the caudate nucleus].
The experiments were conducted on rabbits with chronically implanted electrodes (neocortex, hippocampus, amygdala, caudate nucleus). The rostral part of caudate nucleus was stimulated once daily at a current maximum 300 microA, using 60 Hz square pulses (1.0 Ms) 12.0 s in duration. The severity of motor seizures and its developmental velocity were studied in the relation with a degree of the epileptization of the brain. The data obtained illustrated the next relation: the more stable and intensive were discharges in hippocampus the harder motor seizures.
Animals↗
[2 types of chronic epileptogenesis in rabbits during kindling stimulation of the hippocampus].
The development of convulsant readiness in rabbits during kindling electrical stimulation of the hippocamp was studied as was the dependence of the motor seizure pattern on the degree of epileptiform activity generalization in the CNS. The kindling electrical stimulation of the hippocamp gave rise to the formation in different rabbits of the two main types of afterdischarges. One of them was characterized by high-frequency and high-amplitude spikes (total duration 8-30 s) and the other one by continuous, rather long (50-100 s) hypersynchronous paroxysms. In the interictal period, the animals with the first type demonstrated the occurrence of spontaneous spikes (in all the brain structures under study) that sometimes progressed to a more or less prolonged seizure discharges. At the same time in the animals with the second type of afterdischarges the EEG in the interictal period was slightly different from normal. Despite this fact the seizures induced by electrical stimulation ran a milder course (short-term clonic seizures) in animals with the first type of afterdischarges as compared to those with the second type (long-term clonicotonic seizures). It is assumed that the severity of the motor seizure does not depend on the degree of epileptic activity generalization in the CNS.
Animals↗
[Spontaneous intraictal spikes in rabbits during kindling-type electrostimulation of the hippocampus].
During kindling electric stimulation of the hippocamp, some rabbits demonstrate the appearance of spontaneous interictal spikes (SIS). First they appear in the stimulated hippocamp, then in the contralateral one, and later on in the neocortex. The development of the kindling syndrome depends on the relationship between SIS in the neocortex and hippocamp and the degree of their synchronism. If the amount of SIS in the hippocamp considerably exceeds that in the cortex, the kindling syndrome rapidly progresses. Alternatively, provided that the amount of SIS in the cortex significantly rises and drops at the same time in the hippocamp, the kindling syndrome disappears.
Animals↗
[Syndromes of food hypermotivation in hyperactivity of lateral hypothalamic structures in rabbits].
In experiments on freely moving rabbits a focus of hyperactivity in the initiative centers of food motivation was created by means of blocking the inhibitory mechanisms in the lateral hypothalamus (LH) exposed to tetanus toxin (group I) or chronic electric stimulation (group II). The evoked syndromes were marked by intensity of food hypermotivation. The syndrome provoked by injection of tetanus toxin was characterized by an extremely rapid development, pronounced symptomatology of hyperphagia and severe progress. Concurrently, a pronounced epileptiform activity was recorded in LH, thus indicating the formation of a generator of pathologically enhanced excitation in the "pacemakers" of food motivation. The animals showed completely altered mechanisms of an adequate correction on the behaviour, depending on the results obtained. The syndrome provoked by chronic electric stimulation of LH was characterized by a slower formation and favourable course with a relatively weak epileptiform activity recorded in LH. Food hypermotivation was also demonstrated by the rabbits in the late periods after the commencement of electric stimulation; the adaptive pattern of the animals' behaviour remained unchanged. Occurence of the two syndromes of food hypermotivation is related to the formation of the excitation genertors that differ in the intensity of excitation they produce.
Animals↗
[Increased food motivation in rabbits during prolonged automatic electric stimulation of lateral hypothalamic structures].
An automatic electric stimulation elicited a long-term focus in food motivation centers in rabbits, whose food-getting instrumental activity, EEG and some vegetosomatic parameters were studied. The focus induced the epileptiform EEG activity spreading from the hypothalamus up to the cerebral cortex. The food instrumental responses were either abruptly intensified or inhibited depending on the electrode localization. After cessation of the electric stimulation the focus remained without any sign of fading for one month.
Animals↗
[Stable syndrome of reinforced food motivation in rabbits].
In freely moving rats, a chronic focus of excitation was created in the initiative centers of food motivation by longterm subthreshold electric stimulation of the lateral hypothalamus (LH). This stimulation resulted in a progressive formation of a syndrome reinforced by food motivation, which was manifested in a significant increase in the number of food motivation instrumental reactions and in putting on weight. Concurrently the rabbits demonstrated an intensification of the orienting-investigative behavior and general locomotor activity. The syndrome induced was not strongly connected with the beginning of the electric stimulation and persisted without weakening for a long time (2--4 weeks) after chronic electric stimulation was discontinued. By the character of development, manifestations and persistence the syndrome overtly differed from other phenomena of hyperphagia which were obtained by other workers during chronic electric stimulation of LH. It is assumed that at the basis of the syndrome there lies a formaton of a longterm generator of excitation in the "pacemaker" of food motivation.
Animals↗
Intracentral interstructural relationships in the process of kindling electrostimulations of the hippocampus.
The features of the development of hippocampal kindling as a function of intracentral interstructural relationships formed during electrostimulations has been studied in 13 rabbits by means of electrodes chronically implanted in the brain (cerebral cortex, hippocampi, amygdalar nuclei, rostral portions of the caudate nuclei). The interstructural relationships were evaluated on the basis of the expressivity of the epileptic activity in various structures of the brain and on the basis of its dependence on the activity in the primary pathological focus. It was shown that in the case of the formation in the primary hippocampal epileptic focus of the pathological determinant (as described by G.N. Kryzhanovskii), which determine the activity of other structures, the kindling syndrome develops rapidly. If, on the other hand, competitive suppressive influences predominate in the interrelationships between the primary and secondary epileptic foci, which was most strikingly manifested between the hippocampal epileptic foci, then the pathological determinant does not form in this region and the kindling syndrome does not develop.
Animals↗
The mechanisms of endogenous control of hepatocyte proliferation are different in mice of two inbred strains (BALB/c and AKR).
Explore the source record for details and available documents.
Animals↗
Lectin activity in cell walls of wheat seedlings infected with mycoplasma and exposed to low temperature.
Explore the source record for details and available documents.
Acholeplasma↗
[Effect of the hepatocarcinogen ortho-aminoazotoluene on induction of tyrosine-aminotransferase by glucocorticoids in mouse liver].
o-Aminoazotoluene (OAT) suppressed more than twofold the glucocorticoid induction of tyrosine aminotransferase (TAT) in the liver of SWR mice, which are sensitive to the hepatocarcinogenic effect of OAT, but not in resistant AKR mice. The hormone- and DNA-binding activities of the glucocorticoid receptor (GR) were not affected in either line. The OAT-dependent suppression proved to be associated with a decrease in the DNA-binding activity of HNF3 in liver cell extracts. The content of the HNF3 mRNA did not change, suggesting a posttranscriptional effect of OAT.
Animals↗
[Pulmonary carcinogenesis susceptibility-associated single-nucleotide polymorphisms in K-ras intron 2 affect the binding of factor Gata-6 but not gene expression].
The sequence of K-ras intron 2, which has been associated with lung tumor susceptibility in inbred mouse strains, was analyzed in susceptible strain GR and in resistant strains PT and UT. In the latter case, the intron had a tandem repeat of a 37-bp sequence with variant GC of its two single-nucleotide polymorphisms (SNPs), as earlier reported for resistant strains AKR, C57BL/c, and C3H/A. Strain GR did not differ in intron structure from susceptible strains A/He and ICR, having one copy of the 37-bp sequence with SNP variant CA. By gel retardation assay, a DNA probe corresponding to "susceptible" allele CA of K-ras region 278-307 formed an additional complex with nuclear proteins extracted from the lungs, as compared with probes corresponding to the "resistant" GC and "intermediate" CC alleles. With specific antibodies, the protein binding to the susceptible allele was identified as transcription factor GATA-6. Reverse transcription with subsequent multiplex PCR did not reveal a significant difference in K-ras expression for susceptible and resistant strains. The results suggest that SNPs of K-ras intron 2 do not affect the level of K-ras expression but do control the binding of GATA-6, which plays an important role in lung differentiation.
Animals↗