Effect of dietary protein on proteolytic activities in the pancreatic tissue and contents of the small intestine in rats

The time-courses of proteolytic activities in pancreatic tissue and the contents of the small intestine (the intestinal contents) were determined in rats maintained on a diet containing 30% of various proteins after a switchover from a diet containing 12% casein. 1. The proteolytic activity of the pancreatic tissue quickly responded to change of dietary proteins--within 1 to 6 days--with respect to organ weight, nitrogen content and proteolytic activity, in rats receiving diets containing 30% casein, ovalbumin, lactalbumin, gluten, gelatin or zein. 2. However, the proteolytic activity in the intestinal contents did not necessarily coincide with the pancreatic digestive function; an approximately threefold increase of enzyme activity was demonstrated on the fifth day of feeding in rats receiving gluten. 3. The proteolytic activity in the intestinal contents returned to the initial level on the eighth day in the gluten-fed rats, but those rats maintained on a lysine-supplemented gluten diet exhibited no such elevation of proteolytic activity. 4. No significant difference in pancreatic composition was shown up to the eighth day between the group receiving gluten alone in diet and that receiving the same diet but supplemented with lysine, under the condition of equally restricted food intake. Intestinal trypsin and chymotrypsin levels, however, were higher in the gluten-fed rats, suggesting that the depressed rate of enzyme inactivation in the small intestine might be the principal cause of the finding described under (2) above.

Gibberellin-antagonizing protein in dwarf peas

Seedlings of dwarf pea grown under red light for 9 d were homogenized in 0.1 M phosphate buffer (pH 6.8) and a "water-soluble extract" was obtained by centrifugation, dialysis and lyophilization. The extract contained a proteinaceous substance (or substances) which interfered with the GA3 response of dwarf peas, probably due to complex formation with the hormone.

Starfish gonad: action and chemical identification of spawning inhibitor

The gamete-shedding substance obtained from the radial nerves induces spawning when it is applied to the gonads of mature starfish in vivo and in vitro. A substance that inhibits the action of this spawning factor is present in both ovary and testis; it has been isolated from testis of Asterina pectinifera and chemically identified as L-glutamic acid.