Studies on methods for the determination of amino acid requirements for metabolic balance based on the oxidation rate of 14C labeled lysine to 14CO2]

Male experimental rats (100 gm liveweight) were distributed into 10 groups of 8 animals each and received balanced diets, with the exception of lysine which was added to the diets in graded amounts in such a way that the lysine content of the diets ranged from 2.44 to 5.92 gm/16 gm N. After a feeding period of 7 days the animals received 3H- and 14C lysine injected intraperitoneally, 4 animals of each group were investigated for the total CO2 excretion and 14CO2 excretion during the first 2 hrs after the injection and for the urinary excretion of radioactivity (48 hours). The remaining animals in each group were used for determining the plasma amino acids and for establishing the specific radioactivity of free lysine in the liver and muscles after an 1-hour incorporation period. Total CO2 excretion was not found to be influenced by the lysine contents while the level of excretion of 14C activity through CO2 and that of specific 14C activity of CO2 increased with increasing lysine concentrations. This produced a broken curve pattern, showing an increased release of 14CO2 (under maintenance conditions) if the diet contained 4 gm lysine/16 gm N and more. Investigations for the specific 14C activity of free lysine in the liver, the main site of lysine oxidation, showed that the increase in 14CO2 release was due to an enhanced rate of lysine catabolism and was not brought about by changes in the pool volume or in specific radioactivity. The levels of urinary 14C excretion were not found to be related to the lysine content of the diets, whereas the curve pattern of 3H excretion observed 5 to 8 hrs after injection was similar to that of 14CO2 excretion. The lysine content of blood plasma and the content of free lysine in the liver increased continuously with increasing levels of dietary lysine. The methodological studies made in the present paper showed that in scientific research a determination of amino acid requirements on the basis of CO2 oxidation data may be a very exact and sensitive method. It will also yield values for maintenance requirements.     

Relation between 15N excretion in feces following oral 15N urea administration and blood urea concentration in relation to raw fiber intake in swine

9 pigs of a live weight at the beginning of the experiment of 33 kg received in 3 consecutive series of experiments (3 animals/group) a basic barley ration of 1.0-1.2 kg per animal and day. In groups 1 to 9 the following supplements were given: 1 = without N-supplement, 2 = 10.5 g urea, 3 = 79 g dried skim milk, 4 = 11 g urea, 5 = without N-supplement, 6 = 110 g horse bean coarse meal, 7 = without N-supplement, 8 = 95 g dried skim milk, 9 = 120 g horse bean coarse meal. In groups 1-6 the ration was supplemented with 150-165 g DM partly hydrolysed straw meal per animal and day. After 20 days the animals received a single dosis of 0.5 g/kg0.75 15N-urea (72.1 atom-% 15N-excess) with the morning meal of the first day of the experiment. During the four days of the experiment groups 1-6, due to the straw meal supplement, excreted significantly higher N-amounts than the corresponding groups 7-9. In comparison with the first day of the experiment (1 h after the morning meal) urea concentration in the blood decreased to the following percentage in the sequence 1-9: 64; 65; 77; 54; 64; 73; 82; 88; 84 on the second day of the experiment (1 h before the evening meal. Between the excretion of 15N-excess in faeces (y = mg) during the four days of the experiment and the concentration of urea in the blood (x = mmol/l) there was the following significant negative correlation: y = -40.1 X +340.(ABSTRACT TRUNCATED AT 250 WORDS)     

Experimental infection of normal and immunosuppressed pigs with Pseudomonas pseudomallei

A single dose of 5 x 10(8) bacilli of Pseudomonas pseudomallei by intratracheal injection resulted in acute (21 cases) or chronic (19 cases) melioidosis in 40 of 48 pigs. Fifteen (10 acute and 5 chronic) had been immunosuppressed by cyclophosphamide before inoculation. The major clinical signs were initial fever, marked neutrophilia and, in the acute cases, respiratory distress. There were no signs of the nasal and ocular discharge, paresis or diarrhoea seen in acute cases in south-east Asia. The cyclophosphamide treatment caused a significant decrease in the neutrophil count by 7 d after inoculation in all 15 immunosuppressed pigs, and all were culture positive at necropsy. Eight of the 33 non-treated pigs were culture negative at necropsy. Pigs overcoming the initial phase of infection had more abscess-like nodules that were bacteriologically sterile at necropsy than the pigs with acute cases of melioidosis. P. pseudomallei was isolated predominantly from the spleen, lungs and the injection site. Although only one strain was used in this study, it is likely that Australian strains of P. pseudomallei are not as virulent as the south-east Asian isolates.     

Resorption and incorporation of radioactive-labeled amino acids during the administration of various protein carriers in rats. 2. Uptake of radioactivity by tissues of the gastrointestinal tract after intragastric administration of 14C-L-U-leucine and 3H-glycine]

Male Albino rats (weighing 90-100 gms) were fed ad libitum for 14 days with limited periods of access to food. Powdered whole egg (V), fish meal (F), yeats (H), and gelatine (10% protein in dry matter) used as protein sources. Additionally, one group of rats received a protein-free (e). Radioactive tracers were administered by intragastric infusion of 25 mu Ci 3H glycine and 5 mu Ci 14C L-leucine per 100 gm of body weight 2 hrs after the feeding of 2 gm of the experimental diet per 100 gms of body weight. The level of uptake of radioactive tracers from the different sections of the gastro-intestinal tract was measurels of 3H and 14C labelling in intestinal tissues were observed 3 hrs and 7 hrs after infusion. The level of 14C labelling was found to be negatively correlated and the level of 3H labelling was positively correlated with the biological value of the diet. Intestinal tissues are capable of storing considerable amounts of 14C radioactivity. So, 72 hrs after infusion, the following levels of 14C radioactivity (expressed as percentage of the total dose of radioactivity) were found in tissues of the gastro-intestinal tract: whole egg: 8.4%, fish meal: 9.6%, yeast: 13.1%, gelatine: 14.9%; protein-free diet; 14.2%. The quotients correlating the levels of radioactivity from the intestinal contents with that found in the intestinal wall suggest that the walls of the small intestine possess a high capacity for absorption. At all times of radioactive measurements the walls of the small intestine were found to contain higher levels of both 14C and 3H radioactivity than the contents of small intestine.