Action of endogenous prostaglandins on postprandial pyloric motility: a possible modulation by fats.

The involvement of endogenous prostaglandins (PGs) and the effect of exogenous PGs on the myoelectrical activity of the pylorus were examined for 6 hours after a meal in dogs chronically fitted with intraparietal electrodes on the gastroduodenal junction. The animals received either a standard meal or a fat meal which consisted of canned food added or not (standard meal) with arachis oil. The cyclooxygenase inhibitors, indomethacin (1 mg/kg) and piroxicam (0.2 mg/kg) given prior a fat meal significantly increased the frequency of pyloric spike bursts but did not modify the pyloric motility associated with a standard meal. Synthetic derivatives of PGE1 (misoprostol, 5-10 micrograms/kg) or PGE2 (enprostil 0.5-1 micrograms/kg) reduced the frequency of pyloric contractions after a fat but not a standard meal. It is suggested that both endogenous and exogenous prostaglandins may modulate postprandial pyloric motility when fats are present in sufficient amount into the meal.     

Role of gastrin in duodenal mechanisms of inhibition of gastric secretion in the dog and man

Gastrin serum levels after acidification of the second portion of the duodenum were studied, in dogs and humans, while simultaneously measuring secretin levels and gastric acid secretion. After duodenal acidification in dogs, a 50% inhibition of gastric acid secretion with parallel 100% increases in the serum secretin levels was noted whereas gastrin serum levels did not change (after duodenal acidification). In humans, a 25% inhibition of gastric acid secretion with parallel 50% (not significative) increases in the secretin serum levels was noted. In the entire group gastrin levels did not change, but in 35.2% of the subjects a little increment without statistical significance was noted. It is concluded that the inhibition mechanism of gastric acid secretion after duodenal acidification is more important in dog than in man, and that, probably, gastrin does not play an important role in this mechanism.     

Nitrogen regulation system of Klebsiella aerogenes: the nac gene.

In Klebsiella aerogenes, the product of a his-linked gene, nac, appears to play a crucial role in tying the synthesis of enzymes activated or repressed by ammonia deprivation, such as histidase and glutamate dehydrogenase, to the known regulators of nitrogen assimilation, the products of glnG and glnF.     

Parasitism byAphidius ervi (Hym.: Aphidiidae): Preference for pea aphid and blue alfalfa aphid (Hom.: Aphididae) and competition withA. Smithi

The pea aphidAcyrthosiphon pisum (Harris) and the blue alfalfa aphidA. kondoi Shinji are pests of alfalfaMedicago sativa L. worldwide. The parasitoidAphidium ervi Haliday attacks both species andA. smithi is host specific to pea aphid Experiments were conducted to determine the preference ofA. ervi forA. pisum andA. kondoi at three densities of hosts using the percentages of parasitism and superparasitism, and the distribution of eggs among hosts as criteria. Also examined was the outcome of competition between the two parasitoids when exposed to the same hosts. A. ervi attacks moreA. pisum when provided alone (no choice test) and when provided together in equal numbers withA. kondoi (choice test). There was no significant difference in the number of progeny produced by either parasitoid when a female of each species was introduced simultaneously into the same test unit containingA. pisum hosts. The effects of the pathogenPandora neoaphidis on this competition is reviewed.     

Central origin on the excito-motric action of morphine on intestine]

In ewew fitted with a cerebro-ventricular cannula and equipped with extra-cellular bipolar electrodes on the antrum and proximal small intestine, an intraventricular injection of morphine at a dose (40 micrograms/kg) ineffective peripherally was followed within 1 min by an increased spike activity of the duodenum without disruption of the occurrence of migrating myoelectric complexes. This effect was paralleled by a reduction of antral motility and abolished by small intraventricular doses of nalorphine. After an intravenous injection of large doses of the drug drug (0.8 mg/kg), spike activity was increased at both jejunal and duodenal level without changes in the antrum and followed by a long-lasting disorganization of the motor profile. The results suggested a centrally mediated gastro-duodenal effect of morphine.     

Propagation of myoelectric complexes and intestinal resection in dogs]

The velocity of propagation of the myoelectric complexes was studied in dogs after a single and a double transection of the jejunum. Results were compared with those obtained when a 50 cm segment of the bowel was isolated or removed. After a single transection, the passage through the anastomosis occurred with a delay of 15 min. The delay at this level was more than doubled when a second transection was performed 50 cm aborally, the total delay being then 65 min for the passage through the two anastomoses. After removal or isolation of a 50 cm jejunal segment, the delay was reduced to 45 and 49 min respectively.