Hemopoietic perturbations were observed in gravid beagles subjected to whole-body ionizing radiation during midpregnancy followed by the additional trauma of surgery, with alterations in peripheral blood hemogram parameters, bone marrow morphology, and concentration of marrow-derived granulocytic- and erythrocytic-committed stem cells. However, the trauma of surgery combined with irradiation had no apparent effects on the contralateral uterine horn with the remaining pups, with no indications of miscarriage, absorption of pups, or other complications of pregnancy.

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On day 33 of gestation, foetal beagles were irradiated in utero (0.9 Gy of 60Co gamma-irradiation, 0.4 Gy/min). Foetal haematocytopoiesis was studied during the third trimester of gestation (days 42-55). Peripheral blood nucleated cell counts were 33 per cent lower than normal on day 44 and continued to be lower until day 49, when values became higher than normal. Splenic cellularities of irradiated pups on day 44 were more than 3 times those of the nonirradiated, but thereafter they were similar to normal. Differences in haemopoietic progenitor cell activity between irradiated and normal foetuses were observed. In comparison with the other foetal tissues, the foetal liver appeared to experience greater radiation injury. For example, on day 44, the irradiated liver BFU-E, CFU-E, and GM-CFC per 10(5) cells were almost fivefold lower than normal values. Spleens of irradiated foetal beagles contained a marked increase in all haemopoietic progenitor cells (BFU-E, CFU-E, and GM-CFC) and recognizable proliferative granulocytic cells and nucleated erythroid cells. The haemopoietic activity of the irradiated bone marrow during days 42-44 was similar to that of the irradiated spleen, and compensated for the damaged liver. However, unlike the irradiated spleen, the irradiated bone marrow had decreased BFU-E activity compared with the values for the nonirradiated bone marrow during days 48-55. Until day 50, the irradiated marrow contained fewer recognizable proliferative granulocytic cells but more nucleated erythroid cells.

The area postrema (AP) is being widely studied to delineate its role in such varied functions as blood pressure regulation, conditioned taste aversion, water and energy balance, and radiation-induced emesis. This paper describes the preoperative preparation, surgical procedure, and postoperative care of cats kept long-term in which the AP was lesioned by electrocautery. A dorsal midline approach under gas anesthesia allowed access to selectively lesion the AP. Cats fully regained consciousness the same day and many became homeostatic within 24-48 h. Results of experiments using this model demonstrate the usefulness and effectiveness of the technique for model preparation.