The lowering of the viscosity of DNA solution was caused by the action of AsA or EA and facilitated in the presence of Cu2+. However, the action of AsA-3-P was very weak. By sucrose density gradient centrifugation, it was observed that single- and double-strand scissions of DNA were provoked by AsA or EA and enhanced with Cue, while only a single-strand scission was caused by AsA-3-P and Cue+. Similar action of AsA or AsA-3-P was also observed for RNA, Thus, the result indicates that the enediol group of AsA takes an essential part in the breakage of nucleic acids, and Cue2+ enhances the action. It was shown that Apu was mainly decomposed by AsA, whereas Apy not, suggesting that some pyrimidine cluster may be one of the regions attacked by AsA. During the reaction with DNA, the reducing activity of AsA decreased first to some extent and then increased, whereas the reducing activity of AsA-3-P was much lower than that of AsA and decreased steadily. The priming activity of DNA for DNA polymerase was changed after treatment with AsA according to the condition. It was enhanced when DNA was treated under mild conditions but decreased with severer action.
The characteristics and location of rat intestinal proteins with calcium binding properties were reexamined using both a 45Ca-equilibrated Sephadex G-100 column and the chelex 100 method in the assay of 45Ca binding activity. The rat intestinal mucosa was found to have three different proteins with calcium binding properties. Two of these proteins were found to be vitamin D-dependent and were examined in detail. Thee larger vitamin D-dependent protein, found predominantly in the jejunum and ileum, had a molecular weight of 27, 000 and demonstrated low affinity for calcium; the detection of this protein by the chelex 100 assay was very difficult. The smaller vitamin D-dependent protein, which was associated mainly with duodenum and jejunum, had a molecular weight of 12, 500, and demonstrated a high affinity for calcium.
The mechanism of inactivation of a single-stranded DNA phage, δA of Escherichia coil, by AsA was investigated as a part of the study on the mechanism of inactivation of viruses by AsA. Bubbling air or oxygen gas through the reaction mixture, and the addition of oxidizing agents or transition metals into the reaction mixture enhanced the inactivation of the phage by AsA. In contrast, nitrogen gas bubbling, and the addition of reducing agents, chelating agents or radical scavengers prevented inactivation. The rate of inactivation was faster in the AsA solution preincubated for several minutes than in the freshly prepared AsA solution. DAsA, an oxidized form of AsA, demonstrated little ef-fect on the activity of the phage. Concentrations of hydrogen peroxide which were theoretically produced by the autoxidation of AsA had no effect on the phage. The results indicated that the free radical intermediates produced during the course of the autoxidation of AsA participated in the inactivation. The radicals attacked the DNA of the phage to introduce strand scissions in the DNA, which might be mainly responsible for the inactivation.
Both caffeine and theophylline, which were known to be potent inhibitors of cyclic-AMP phosphodiesterase, stimulated the incorporation of myoinositol into phosphatidylinositol in rat liver homogenate. However, cyclic-AMP had no effect. The effect of dibutyrylcyclic-AMP differed with different concentrations. These results suggest that the stimulation cannot be explained by the increase in the amount of cyclic-AMP. This view was supported by the fact that papaverine, cyclic-AMP phosphodiesterase inhibitor, did not stimulate the incorporation and imidazole, the phosphodiesterase stimulator, did not inhibit the incorporation, and that adenylcyclase stimulators, epinephrine and glucagon, did not stimulate the incorporation.
Synthetic 1α-hydroxycholecalciferol (lα-OH-D3) was given intravenously in a dose of 2.5-10μg per day to three patients with chronic renal failure. As little as 10μg of lα-OH-D3 daily for a week improved intestinal calcium absorption to a normal level, raised serum calcium, and reduced serum alkaline phosphatase. Severe rickets which had not responded to large amounts (>200mg in total) of vitamin D2 was markedly cured with 2.5μg of lα-OH-D3 given daily for 3 weeks. These clinical data hold promise that lα-OH-D3 is certainly useful in the improvement of intestinal malabsorption of calcium and bone diseases in renal failure.
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.
The effect of protein deficiency on the rate of loss of radioactivity from body constituents was studied in adult rats administered 14C-Chlorella protein hydrolysate or 14C-lysine. Rats were kept on a protein-free diet for 3 weeks and then injected with labelled amino acids and fed on a protein-free diet for 3 more days to allow 14C deposition in tissues. Then they were given experimental diets (protein-free diet, 1% and 10% wheat gluten diets pair-fed with the protein-free diet, and 10% wheat gluten diet ad libitum) for 7 days and sacrificed. The rates of loss of radioactivity from tissue proteins became low in general with the extent of protein deficiency. This increased capacity of tissues to retain 14C-amino acids may result from higher efficiency of protein utilization in protein deficiency. The reutilization of free amino acids and the rate of catabolism of tissue proteins are discussed on the basis of the results. The half-life of muscle protein was too long to observe the effects of experimental diets given for 7 days on the rate of loss of radioactivity.