title: Fractionated irradiation and haematopoiesis. I. The effect of a differently fractionated radiation dose of 600 R.
abstract: The effect of the same dose of irradiation (600 R) divided into two different fractions (500 + 100 R; 400 + 200 R; 300 + 300 R) upon the haematopoietic system of young rats (25 days old) was investigated. Free interval between the first and the second dose was 5 minutes. Changes were observed in bone-marrow, spleen and blood in all the experimental groups of 10 days after the irradiation. Spontaneous regeneration of haematopoiesis after a single dose of 600 R is higher than after division of this dose into two fractions, excluding the group where the dose was divided into two equal fractions. The most intensive haematopoietic repopulation was found in the group of rats irradiated with 300 + 300 R, where the primary dose was the smallest. In fractional conditions, the first dose is of primary importance for the repopulating capacity of the haematopoietic system regardless of the short free interval.
mesh_terms: D000818:Animals; D001769:Blood / Q000528:radiation effects; D001853:Bone Marrow / Q000528:radiation effects; D005260:Female; D006410:Hematopoiesis / Q000528:radiation effects*; D008297:Male; D011829:Radiation Dosage; D051381:Rats; D013154:Spleen / Q000528:radiation effects; D013997:Time Factors