Activity of protein kinase A and gustatory responsiveness in the honey bee ( Apis mellifera L.).

The cAMP-dependent protein kinase A is involved in the induction of long-term memory and habituation in the bee. Gustatory responsiveness correlates strongly with associative and non-associative learning in bees. We tested whether protein kinase A activity in the antennal lobes correlates with gustatory responsiveness. Thirty minutes after feeding, bees with high gustatory responsiveness had a significantly higher protein kinase A activity than bees with low responsiveness. Ninety minutues after feeding, when gustatory responsiveness had increased in initially unresponsive bees, no changes in protein kinase A activity were found. We also tested time-dependent effects of protein kinase A activator and protein kinase A inhibitor on gustatory responsiveness. Injection of the protein kinase A activator adenosine 3'5'-cyclic monophosphate 8-bromo-sodium salt or of the protein kinase A inhibitor KT 5720 did not affect gustatory responsiveness within the first 4 h after treatment. Feeding of adenosine 3'5'-cyclic monophosphate 8-bromo-sodium salt over 4 days increased gustatory responsiveness in newly emerged bees and adult foragers. These results enable us to distinguish between two different forms of gustatory responsiveness: basal and transient gustatory responsiveness. Basal gustatory responsiveness correlates with protein kinase A activity and can only be modulated in the range of several days. Transient gustatory responsiveness appears to be independent of protein kinase A activity and can be modulated in the range of minutes to hours.

The effect of exogenous substrate on hepatic metabolism and membrand transport during endotoxemia.

Endotoxemia in dogs reduced hepatic uptake and biliary excretion of indocyanine green dye. This diminished active membrane transport was associated with reduced hepatocyte membrane potential difference. Studies of arteriovenous concentration differences and flow across the liver demonstrated that endotoxemia increased hepatic glucose and lactate production and decreased oxygen consumption. Correction of this energy deficit occurred following infusion of glucose and insulin, but not after administration of isocaloric quantities of intravenous amino acids. The glucose-insulin infusion during endotoxemia shifted the liver back to an organ of glucose uptake, improved oxygen consumption, and provided the necessary energy for normal dye transport and maintenance of the normal membrane potential difference.

Reversal of severe fatty hepatic infiltration after intestinal bypass for morbid obesity by calorie-free amino acid infusion.

Hepatic fatty infiltration complicating jejunoileal bypass can be massive and may require restoration of gastrointestinal continuity. This fatty infiltration appears to be caused by protein depletion associated with adequate or high carbohydrate intake. The present study has shown that calorie-free amino acid alimentation can reverse these changes. In three of thirteen patients who underwent 12 inch to 6 inch jejunoileal bypass procedures, symptomatic hepatomegaly developed with near total replacement of hepatocytes by massive fatty infiltration. After undergoing liver scan, liver biopsy, and liver function tests, the patients were started on a peripheral infusion of 2L per day of a 4.25 per cent crystalline amino acid solution, allowing for fat mobilization while preserving body protein stores. All oral intake was withheld except for water. At the end of a fourteen to twenty-one day infusion period, serum albumin levels increased by 1 gm in all patients. Decreases in liver volume of 83, 45, and 40 per cent occurred. During the infusion period ketonuria was 4 plus in all patients indicating active lipolysis. Weight loss was impressive (17, 19, and 40 pounds). All patients showed marked symptomatic improvement, and postinfusion liver biopsy specimens showed a return to near normal architecture. Maintenance of normal liver size by a high-protein, low-carbohydrate diet was observed in a five to seven month follow-up period. In contrast to previous studies using standard hyperalimentation solutions, the use of calorie-free amino acid solutions reverses the hepatic fatty infiltration seen after intestinal bypass by mobilization of fat. This fat mobilization does not occur as readily in the presence of large amounts of glucose.