Acute radiation sickness--morphology of CNS syndrome

The present treatise is a report on the study of morphologic changes induced in the brain of laboratory animals by the exposure to supralethal doses of ionizing radiation. The review of literature summarizes the basic current findings on the interaction between biological objects and ionizing radiation. Principal attention is then paid to literary data describing the morphological changes in the single components of the central nervous system after irradiation. There is a detailed account primarily of what has so far been known on the structure of the blood-brain barrier and its individual, morphologically observable components. What the exploration of literature shows is that problems concerning the morphologic changes following supralethal irradiation have hitherto been paid but little attention. The scarce publications on this topic mostly offer contradicting conclusions. Most of the experiments were made with conventional female rats supplied by the firm Velaz. The animals were exposed to 60Co gamma radiation doses within the range of 15 to 960 Gy. The material for study was sampled in the intervals from 15 min to 6 days after the irradiation had ended. Similar experiments, though on a smaller scale, were carried out with mice, rabbits and dogs. The tissue samples were treated in current methods for the purposes of light microscopy, electron microscopy and histochemistry. The light microscopical pattern of morphological changes during the first hours is dominated by the signs of a cerebral edema. The nerve cells show symptoms of acute swelling. There are small hemorrhages near some of the capillaries. In later periods, the nerve cells assume the nature of pyknomorphous neurons. The degree in which the changes are expressed however varies considerably. Dystrophic changes were also found for glial cells. Small hemorrhages are dispersed over all the areas of the brain. There are persisting signs of brain edema with dilated perivascular and pericellular spaces. The activities of the following enzymes were studied in histochemical examinations: acetylcholinesterase (ACE), nonspecific cholinesterase (CE), alkaline phosphatase (AP), acid phosphatase (AcP), ATP splitting enzyme (ATP), thiamine pyrophosphatase (TPP), glycero-3-phosphate dehydrogenase (GPDH), succinodehydrogenase (SDH), acid nonspecific esterase (AE). A phase progress of activity changes was found for AP, CE, and ACE in the blood capillaries of the brain cortex after the exposure to the radiation doses of 50 to 200 Gy. The irradiation was first followed by elevation of their activity and then, in the intervals of 4 to 24 hours after irradiation, by a drop in their activity below the level obtained for the control animals.(ABSTRACT TRUNCATED AT 400 WORDS)