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PubMed1984

Nonstochastic effects of different energy beta emitters on the mouse skin.

The effect of irradiating varying areas of mouse skin from 860 down to 0.8 mm2 with different energy beta emitters was studied to clarify protection problems of localized doses to the skin. Both 90Sr and 170Tm sources show area effects for dose-response curves. The 90Sr doses that produced moist desquamation in 50% of irradiated fields (MD-50 doses) were 22, 42, 70, and 1000 Gy for 400-, 95-, 20-, and 0.8-mm2 sources. The MD-50 doses for 170Tm were 50, 54, 90, and 170 Gy for 860-, 64-, 20-, and 3.1-mm2 sources. Thus for the larger 170Tm sources there is much less area effect. There was no significant difference in effect between the different energy 90Sr and 170Tm sources for moist desquamation. A simple hypothesis based upon the repopulation of epithelial cells from the edges of the irradiated field and/or from surviving follicle basal cells can explain these area and energy effects in the mouse and in parallel pig skin experiments. The doses needed for 50% of the mice to show ulceration after 64-, 20-, and 3.1-mm2 170Tm sources were 260, 550, and 8300 Gy, respectively, while those for 90-, 20-, and 0.8-mm2 90Sr sources were 150, 210, and 3100 Gy. Thus there is a definite area and energy effect for these sources for this deep dermal damage. The steep rise in dose needed to produce given skin reactions for the smallest area (0.8 mm2) should reassure those faced with assessing the hazard of sub-millimeter-sized particles in/on human skin.

Animals↗
PubMed1984

Nonstochastic effects of different energy beta emitters on pig skin.

Circular areas of pig skin from 1- to 40-mm diameter were irradiated with beta emitters of high, medium, and low energies, 90Sr, 170Tm, and 147Pm, respectively. The study provides information for radiological protection problems of localized skin exposures. During the first 16 weeks after irradiation 90Sr produced a first reaction due to epithelial cell death followed by a second reaction attributable to damage to the dermal blood vessels. 170Tm and 147Pm produced the epithelial reaction only. The epithelial dose response varied as a function of beta energy. The doses required to produce moist desquamation in 50% of 15- to 22.5-mm fields (ED50) were 30-45 Gy from 90Sr, approximately 80 Gy from 170Tm, and approximately 500 Gy from 147Pm. A model involving different methods of epithelial repopulation is proposed to explain this finding. An area effect was observed in the epithelial response to 90Sr irradiation. The ED50 for moist desquamation ranged from approximately 25 Gy for a 40-mm source to approximately 450 Gy for a 1-mm source. The 5-, 9-, and 19-mm 170Tm sources all produced an ED50 of approximately 80 Gy, while the value for the 2-mm source was approximately 250 Gy. It is also suggested that the area effects could be explained by different modes of epithelial repopulation after irradiation. After high energy beta irradiation repopulation would be mainly from the field periphery, while after lower energy irradiation repopulation from hair follicle epithelium would predominate.

Animals↗
PubMed1981

Microspheres in cardiac lymph: control and ischemic states.

The cardiac lymph from conscious animals was monitored for the presence or absence of radiolabelled 15 micrometer microspheres during: 1) control periods after left atrial injection of microspheres and b) after circumflex coronary artery (CFX) occlusions (10--20 min total or less than 40 mins 50% of control flow) followed by full reperfusions. Microspheres (15 mu) numbering 7--150 were present in the lymph within 2 hrs after the occlusions; and in three experiments, the presence of a small number in the lymph on the following day implied continual release overnight. No microspheres were present in 8--48 hr lymph samples prior to occlusions. This study suggests that some microspheres escape from the intravascular space of the myocardium and are channeled into the cardiac lymphatics; this is apparent even after short-term ischemic events.

Animals↗