The effect of a high-intensity radiation exposure on the brain function of monkeys. The postradiation changes in brain bioelectrical activity

In experiments with Macaca fascicularis it has been found that changes in the total bioelectric activity of the brain within the EEG range that occur during the first 60 min following whole-body irradiation with a dose of 45 Gy (6.5 Gy/s) are interrelated with the dynamics of nervous and psychic activity of the exposed animals, exhibit a definite stereotype of their development (disorganization of rhythms: generalized synchronization of biopotentials; and development of synchronous processes), and coincide in time with the main stages of the development of the clinical picture of the acute postirradiation period (noncoordinated stimulation, sopor or coma, and partial recovery).     

The effect of a high-intensity radiation exposure on the brain function of monkeys. The postradiation changes in the EEG response to rhythmic photostimulation]

In experiments with monkeys (Macaca fascicularis) it has been shown that whole-body irradiation with a dose of 45 Gy (6.5 Gy/s) causes considerable changes in the EEG response to rhythmic photostimulation (PS). These changes are: reduction of the desynchronizing effect of PS with regard to a background rhythmicity; decrease in the reception rate of the rhythms of light flashes (RLF); narrowing of the RLF frequency range; and increase in the reaction momentum. The postirradiation changes in the EEG response to PS are considered as a manifestation of inhibition of the cortex functional activity and impairment of sensory information processing in the brain.     

Some changes in bioelectrical activity of the brain during short regulated exposure to pulsed electrical fields

It was shown that short (10 s) exposures of white rats being at rest to impulse (1 ms) electromagnetic fields (170 A/m) at a fixed frequency of pulse sequence in the range of the theta-rhythm do not change the contribution to the electrocorticogram (ECoG) of the harmonic whose frequency corresponds to the frequency of pulse sequence. By contrast, treatments with a frequency-pulse modulation at which the interpulse intervals corresponding to the frequency of the harmonic being studied were not observed throughout the range of exposure but at which their high correlation was provided, assisted in decreasing the contribution of the harmonic to the ECoG spectrum. If the functional state of the central nervous system was changed by drugs leading to the predominance of the short-wavelength activity in the ECoG, both regimes of exposure significantly affected the contribution of the harmonic in the ECoG, whose direction and dynamics depended on the excitability of neurons.     

Phenomenology and genesis of changes in the total bioelectrical activity of the brain in response to electromagnetic radiation

A review of the date on phenomenology and genesis of changes in overall activity of brain in response to electromagnetic radiation is presented. It is validated the nonspecific synchronizing influence of the considered factor. This influence can be a reason of epileptoid class convulsions under growth of its biological significance as an irritant of central nervous system.     

Postradiation changes of active ion transport systems of the CNS. The effect of superlethal doses of ionizing radiation on the Na,K pump in surviving brain slices

Active potassium ion transport in surviving sections of rat brain was irreversibly inhibited 6 min, 1 h and 6 h following whole-body single X irradiation. At the same time, the accumulation of products of lipid peroxidation and phospholipase hydrolysis was followed up during the development of radiation pathology. The relationship was noted between the postirradiation changes in the physicochemical status of lipids of the membrane and the impairment of its transport function.     

Postradiation changes in the systems of active ion transport in the CNS. Potassium ion reaccumulation by surviving brain slices

The data are reported concerning the effects of ionizing radiation (0.155 C/kg, 0.206 C/kg, and 0.31 C/kg), A2 phospholipase and short-chain fatty acids that are indicative of an essential contribution of a membrane lipid component to the effect of radiation on Na-K pump of the neuron and the universality of the mechanisms of action of ionizing radiation on organisms differing in radiosensitivity.     

Mediator processes in the brain structures in the late periods after external and combined exposure to ionizing radiation

In experiments with mature Wistar male rats it was shown that X-radiation of 12.9 mCi/kg and the combined effect of X-rays and 131I of 6.5 mCi/kg changed the rate of mediator processes in the structures responsible for the hypothalamic function regulation. At remote times (6 months) following irradiation differences were observed in the discoordination of mediator interrelations associated with the peculiarities of the indirect effect of external and combined irradiation implemented via endocrine mechanism system.     

Stable chromosome rearrangements in the somatic cells of monkeys subjected to acute radiation exposure

Frequencies of stable chromosome rearrangements in bone marrow cells of rhesus monkeys (Macaca mulatta) have been determined for following time periods: from 0.25 to 6.0 and from 10.0 to 18.0 years after gamma-irradiation at doses of 154.8-167.7 mC/kg. The time of the occurrence of pathological clones and the character of their formation in those cells, whose markers were presented by chromosome rearrangements of the same type, have been defined. Some animals showed the tendency towards the increase in the frequency of uni-type rearrangements in the pathological cell clones. This phenomenon could be a potential precursor of the pathological processes in irradiated individuals.     

The aging brain: protein phosphorylation as a target of changes in neuronal function.

There is evidence that senescence affects neurotransmission at different levels. In particular, this review summarizes the studies on age-dependent modifications in protein phosphorylation, which represents the final pathway in the action of transmitters and hormones at neuronal level. Cyclic AMP-dependent protein kinase and protein kinase C have been reported to be modified during aging in various cerebral areas; the changes may involve either enzyme activity or substrate availability. These findings can be related to the alterations in neurotransmitter function and synaptic efficiency observed in the senescent brain. The activity of the other types of protein kinases (tyrosine-, cGMP-, calcium/calmodulin-dependent) during aging needs to be explored. An emerging point is the role of protein phosphorylation in the transfer of membrane signals to the nucleus, for the activation or disactivation of specific genes responsible for long-term neuronal events. Along this view, alterations in protein kinase pathway during senescence would ultimately affect gene expression, resulting in long term modifications of cell function. The reviewed literature opens the perspective of restoring some of the deficits associated with senescence by modulating protein phosphorylation pathway.     

Rat brain catecholamines in the initial period of acute radiation exposure

Total X-ray irradiation (0.21 C/kg of rats induces an hour later an increase in the dopamine and norepinephrine content in the grey matter by 11 and 60%, respectively. The spontaneous release of dopamine and norepinephrine from the brain synaptosomes of the irradiated rats falls causing a decrease of the initial rate of the process. Potassium chloride depolarization of synaptosome membranes of the control rat brain increases both the maximal and initial rate of the process of neuromediators' release; in irradiated animals only the maximal rate of the process grows, the initial rate of the dopamine release being unchanged and that of norepinephrine increasing but less that in the control. After irradiation maximal rate of the by synaptosomes dopamine uptake is 2.6 times as high, while that of norepinephrine is 4.6 times as low; Km of the highly specific uptake of norepinephrine decreases.     

Acute exposure of rhesus monkeys to DDT: Effect on carbohydrate metabolism

Four furocoumarins, two having a linear molecule, psoralen and 8-methylpsoralen and two having an angular molecule, angelicin and 4,5′-dimethylangelicin were tested for mutagenesis in Escherichia coli B wild type and in various strains deficient in known repair systems. The results indicate that both monoadducts and crosslinks are mutagenic. The mutagenic efficiency of the furocourmarins ranks in the following order 8-methylpsoralen > psoralen > angelicin > 4,5′-dimethylangelicin.