Insulin induced hypoglycemia and tolbutamide administration accompanied by much smaller falls in blood glucose were associated with increased pancreatic vein IRG concentrations in laparotomized dogs under barbiturate anesthesia. Hyperglycemia may have diminished pancreatic IRG release. Changes in IRG levels in peripheral and jejunal veins during hypoglycemia were unremarkable. In dogs, pancreatectomy was associated with no change in IRG release into a jejunal vein. Very small doses of glucagon administered intraportally during hyperglycemia were effective in promoting IRI release. It is concluded that a fall in blood glucose from the basal state is a stimulus, and hyperglycemia is an inhibitor, of pancreatic IRG release. It is possible that glucagon may act in the basal state to deliver repeated small pulses of glucose and insulin into the circulation.

The study hereby submitted has been designed to show whether there are any differences between using a conventional knife or a CO2-laser when excising and grafting tumors in animal experiments. The animals were C57B1/6 mice, the tumor was the Lewis lung carcinoma. Eight days after tumor inoculation into the s.c. layer of the back, 213 mice were treated by tumor excision either with a conventional knife or a CO2-laser. Eighty-six excised tumors were cut, and the tumor surface was swabbed into the s.c. layer on the nape of 86 tumor-free mice. Survival times of the laser-operated animals were insignificantly longer. However, small tumors showed markedly longer survival times. The interval without recurrence was longer for all tumor sizes when the laser was used (P less than 0.005). The laser method yielded lower growth rates when the tumor surface was swabbed into tumor-free mice (P less than 0.0001). Histological and cytologic tests of the laser-excised and- swabbed specimen demonstrated a high rate of cell destruction. Therefore, the CO2-laser seems to have some significance in cases where the incision is made close to the tumor or where tumor surfaces may be lesioned.

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