Electron microscopic observations of rat medullary reticular tissue after short-term,whole body gamma irradiation

Summary The ultrastructural observations recorded after shortterm, whole body gamma irradiation on medullary reticular tissue were evaluated. Twenty-five adult rats were divided into one control and four irradiated groups which received 1,000 rads, 2,000 rads, 5,000 rads, and 10,000 rads, respectively. Tissue preparations in each group consisted of immersion fixation in veronal acetate buffered OsO₄ and a perfusion technique utilizing s-collidine buffered glutaraldehyde.The micrographs from the control group revealed conformity to neurological ultrastructures as reported by other authors, with one exception. A structure termed concentric membranous body (CMB) was observed in the s-collidine buffered, perfused animals. This structure was noted to be associated with neuronal membranes and to contain laminated repeating intraperiodicity of 40–50Å.In all irradiated groups (1,000, 2,000, 5,000, 10,000 rads) membranous swirls were observed. These structures appeared to be of CMB origin in the lower exposure groups and from both CMB and myelin sheath breakdown in the higher groups. Progressive cytoplasmic vacuolization, mitochondrial, and myelin sheath damage were noted as being related to dose level. Since no apparent capillary bed damage was observed in any irradiated animal, it was concluded that the cellular abnormalities recorded were the result of direct or localized irradiation damage of the brain.Submitted to the Faculty of the Graduate School, Texas A & M University, in partial fulfillment of the requirements for the degree of Doctor of Philosophy.