Levels Of Total Free Amino Acids Research Articles

Cecal Nitrogen Metabolism and Amino Acid Absorption in the Rabbit

Nitrogen balance and weight changes were determined in two groups of rabbits fed diets containing all natural protein or part nonprotein nitrogen from urea. The rabbits were fed the experimental diets for a 10-week period starting at 7 weeks of age. No significant differences in weight gains or nitrogen retention were found between groups. Total nitrogen, ammonia, urea, and free amino acid levels were determined in the contents of several segments of the gastrointestinal tract of the rabbits fed both diets. Significantly less total nitrogen, ammonia, and free amino acids were found in the lower colon compared with the cecal contents of both groups. Subsequent studies with (C)alanine revealed considerable fermentation of alanine in both the cecum and upper colon contents, but there was little absorption into the blood. It was concluded that the disappearance of nitrogen that occurred between the cecum and colon was in the form of ammonia, and that the value of urea as a nitrogen source resulted primarily from tissue synthesis of dispensable amino acids and coprophagy.

Seasonal changes in the free amino acid composition of the adult barnacle, Balanus Balanoides

1. 1. The total free amino acid (FAA) level in Balanus balanoides varied seasonally with a maximum level in the autumn and a minimum level in the spring. 2. 2. Proline, glycine, taurine, arginine, alanine, glutamic acid and serine were the most prominent free amino acids. The level of glycine showed a marked increase in November at the time of fertilization. Alanine had its highest level during the winter when food is sparse and feeding rates are reduced. 3. 3. Barnacles kept without food at 5° and 15°C from October to December had an increased FAA content compared with animals on the shore. There was a marked increase in the alanine content of animals kept at 15°C. 4. 4. Barnacles kept without food at 5°C from January to June had a lower FAA content than animals on the shore. Animals kept at shore temperatures and fed Artemia nauplii from mid-February onwards had a similar FAA content to the shore animals. 5. 5. A survey of aminotransferase activity in B. balanoides showed strong glutamate-pyruvate transaminase (E.C. 2.6.1.2) activity but no glutamate-oxaloacetate transaminase (E.C. 2.6.1.1) activity. Aminotransferases involving the amination of glyoxylic acid to glycine were found to be active.

Variations in aminotransferase activity and total free amino acid level in the body fluid of the snail Lymnaea luteola during different larval trematode infections

The common freshwater snail Lymnaea luteola was found to shed three types of trematode cercariae: the xiphidiocercaria of Prosthogonimus sp., the furcocercaria of Schistosoma incognitum, and an amphistome cercaria, Cercaria pigmentata. Total free amino acid content of the body fluids of snails drops significantly in all three types of infection. The total aminotransferase activity in the body fluid rises significantly in xiphidio- and furcocercarial infections and drops in pigmented cercarial infections. Aspartate aminotransferase (GOT) level increases significantly in all types of infection but not alanine aminotransferase (GPT). Alanine aminotransferase activity shows no significant rise in furcocercarial infection and actually drops in pigmented cercarial infections. These differences in the aminotransferase levels have been explained in terms of the biochemical requirements of the parasites harbored by the snails.