strontium-radioisotopes and Hypoxia

The authors draw attention to the danger of the development of hyperaemia because of the possible influence of free oxygen radicals during the hypoxic period on brain cells. Using radioactive microparticles of 85Sr the authors assessed the cardiac minute volume and blood flow through the medulla oblongata, cerebellum, subcortical area and cerebral cortex in adult laboratory rats 20 hours after 2-minute ischaemia induced by positive radial acceleration of 10 G. The results indicate an increase of the local blood supply in the investigated parts of the brain, although lower than after 8-hour exposure to high altitude hypoxia at 7000 m.

Topics: Animals; Brain Ischemia; Cerebrovascular Circulation; Female; Hyperemia; Hypoxia; Male; Radionuclide Imaging; Rats; Strontium Radioisotopes

The four existing animal models of cyclic hematopoiesis are briefly described. The unusual erythropoietin (Ep) responses of the W/Wv mouse, the Sl/Sld mouse, and cyclic hematopoietic dog are reviewed. The facts reviewed indicate that the bone marrow itself is capable of influencing regulatory events of hematopoiesis.

Topics: Anemia; Animals; Bone Marrow; Bone Marrow Cells; Disease Models, Animal; Dog Diseases; Dogs; Erythropoiesis; Erythropoietin; Hematopoiesis; Humans; Hypoxia; Lithium; Mice; Mice, Inbred Strains; Mink; Neutropenia; Periodicity; Prednisolone; Strontium Radioisotopes

The effectiveness of the radiosensitiser Ro-07-0582 has been tested in man by observing the skin reaction after irradiation using a radio-strontium source with and without administration of the drug. The skin reaction technique has been extended so that skin was irradiated when at low oxygen tension (hypoxic) as well as when fully oxygenated (oxic). Limbs have been made hypoxic by occlusion of the circulation using a sphygmomanometer cuff. To this has been added the prior use of an Esmarch's bandage to reduce the volume of blood in the skin and the enclosing of the limb in a bag of nitrogen. The Oxygen Enhancement Ratios obtained without the sensitiser in nine studies using this system ranged from 1-64 to 2-46. Using Ro-07-0582 skin reactions after oxic exposures were not enhanced but those after hypoxic exposures were markedly increased. The Relative Sensitising Efficiency expresses, as a percentage, the restoration of the sensitivity of cells protected by hypoxia. In six cases where Ro-07-0582 was given in doses ranging from 81 to 165 mg/kg, efficiencies ranged from 27 to 71%. These results can be compared with three studies using metronidazole where efficiencies ranged from 11 to 15%. Using comparable dosage Ro-07-0582 seems approximately three times more effective than metronidazole. In this first study in man, Ro-07-0582 appears to be a highly effective radiosensitiser of hypoxic cells.

Topics: Constriction; Drug Evaluation; Humans; Hypoxia; Metronidazole; Nitroimidazoles; Oxygen; Radiation Dosage; Radiation Effects; Radiation-Sensitizing Agents; Regression Analysis; Skin; Skin Pigmentation; Strontium Radioisotopes

Topics: Animals; Cerium Radioisotopes; Coronary Circulation; Dogs; Extracorporeal Circulation; Hypothermia, Induced; Hypoxia; Microscopy, Electron; Myocardium; Strontium Radioisotopes; Ventricular Fibrillation