Deprivation Of Essential Amino Acid Research Articles

630 RENAL RESPONSE TO ESSENTIAL AMINO ACID DEPRIVATION: ADAPTATION OF TAURINE (TAU) TRANSPORT

TAU behaves as an essential amino acid in the human neonate. Infants fed diets containing virtually no TAU have low [TAU] in plasma and urine (Gaull et al, J. Ped. 90:348, 1977). We reported (Rozen et al, Ped. Res. 14:624, 1980) that control and hypertaurinuric mouse strains, fed a low-protein diet, decrease fractional TAU excretion in vivo and increase TAU uptake by renal cortex slices and purified luminal membranes in vitro. We have now investigated the specificity of the renal adaptation to TAU deprivation. Mature C3H and C57B1/6J mice, fed a selective low-sulfur-amino acid diet for 2 wks., also decrease fractional TAU excretion in vivo (p <0.01) and increase uptake of TAU by renal cortex slices (p <0.01) and by brush border membranes (p <0.01). However, uptakes of glucose and alanine are also increased in the brush-border membrane vesicles of in vivo adapted mice. We then examined the hypothesis that the renal adaptation reflects deprivation of an essential amino acid (methionine). Mature mice, deprived of phenylalanine for 2 wks., also decrease urinary TAU excretion (p < 0.02) and increase uptake of TAU, glucose and alanine by brush-border membranes (p < 0.05). It appears that essential amino acid deprivation is associated with adaptation of the renal transporters for TAU and other solutes. Our findings in the mouse offer an in vitro explanation for the finding (Pentz, Biochem. Med. 2:70, 1968) that the human female decreases urinary TAU excretion during lysine deprivation.

Recovery of Streptococcus mutans after amino acid deprivation.

The recovery of Streptococcus mutans FA-1 in a complete, chemically defined medium was examined after 1, 3, and 6 h of essential amino acid deprivation. Amino acids could be divided into two groups based on their effect on the relative rates of recovery: those amino acids (leucine and cystine) that are precursors of protein only, and amino acids (glutamate/glutamine or lysine) that are incorporated into both protein and cell wall peptidoglycan. Culture turbidity, deoxyribonucleic acid, ribonucleic acid, protein and cell wall peptidoglycan measurements indicated rapid recovery after leucine/cystine starvation periods. However, a 6-h leucine/cystine deprivation resulted in a slower exponential rate of growth (180-min doubling time compared to the normal doubling time of 85 to 90 min) after recovery. Glutamate/glutamine starvation, on the contrary, resulted in greatly extended recovery periods, especially after 3- and 6-h amino acid deprivations. Macromolecular synthesis was most severely affected by 6-h glutamate/glutamine starvation and required 6 to 10 h for recovery of an exponential rate. A delay in the recovery of deoxyribonucleic acid and cell wall peptidoglycan synthesis beyond that of the other macromolecules was observed after 1 and 3 h of deprivation with either leucine/cystine or glutamate/glutamine. However, after a 6-h amino acid deprivation, deoxyribonucleic acid synthesis recovered more rapidly than that of the other macromolecules studied. The results are discussed in terms of the nutritional environment of the oral cavity and its effect on the growth and survival of S. mutans.

Biochemical characteristics of different forms of protein-energy malnutrition: an experimental model using young rats

I. In three separate experiments, four groups of five to eight young male rats were fed either (i) a high-protein diet, for which the net dietary protein:total metabolizable energy ratio (NDp:E) was 0-1 (HP diet); or (ii) a low-protein diet, for which NDp:E was 0-04 (LP diet). In both these groups, food intake was ad lib. In group (iii) the HP diet was given in an amount approximately equal to that taken by the LP group fed ad lib. (HP-restricted). In group (iv) rats were fasted for 48 h after receiving the HP diet (HP-fasted). Each experiment lasted 4 weeks. 2. In the LP and HP-restricted groups, food intake was about 50% of that of the HP rats, while body-weight, after 4 weeks on diet was about 35% and 55% of that of HP rats, for LP and HP-restricted respectively. Both groups of malnourished rats gained some weight during the experiment. 3. Measurements of oral glucose tolerance and plasma insulin levels were made in the fourth week. LP and HP-restricted rats both showed low fasting insulin levels and low insulin to glucose ratios during the glucose tolerance tests; the LP rats were more seriously affected. 4. At the end of the fourth week the rats were killed and blood, liver and gastrocnemius muscle were analysed. LP rats showed specifically and consistently low values for haemoglobin and plasma protein concentration, and low activities of hepatic glucose-6-phosphatase (EC 3-1-3-9) and of alanine aminotransferase (EC 2.6.1.2) in liver and muscle. The activity of hepatic aspartate aminotransferase (EC 2.6.1.1) was, if anything, increased. The plasma amino acid concentrations and ratios showed a specific fall in branched-chain amino acids. Liver fat concentration was consistently elevated. The HP-restricted rats had normal values for haemoglobin, plasma protein andliver fat, and near-normal values for plasma amino acids. Hepatic alanine aminotransferase showed increased activity compared with HP rats, but muscle alanine aminotransferase showed reduced activity. The HP-fasted rats had increased haemoglobin, plasma protein and liver fat concentration, and very low liver glycogen concentrations. Hepatic alanine aminotransferase activity was elevated. Plasma alanine concentration was specifically reduced. 5. The results are consistent with suppression of gluconeogenesis, liver dysfunction and essential amino acid deprivation in LP rats. These biochemical changes found in rats on a low intake of a diet of low protein and high carbohydrate value are similar to those found in kwashiorkor. An equally low intake of a diet of good protein value (HP-restricted) led to marginally better growth, accompanied by biochemical signs of increased gluconeogenesis, analogous to those reported for nutritional marasmus. This nutritional state was not biochemically identical with that of acute fasting. 6. The results are discussed in terms of the consistency of the rat model, and its contribution to understanding biochemical changes found in infant malnutrition.

Influence of culture conditions on growth of FL-74 cells and feline oncornavirus cell membrane associated antigen production

The FL-74 cell, a feline lymphoblastoid cell line derived from a tumor induced by leukemia virus, grows equally well in static suspension culture (plastic T-flask or silicone treated glass bottles) or in spinner culture. No growth was observed in unsiliconized glass bottles. Although feline leukemia virus production was nearly the same in FL-74 grown in each of the above types of vessel, the expression of the feline oncornavirus membrane associated antigen (FOCMA), as determined by membrane immunofluorescence, was more intense and more complete on cells grown in static suspension. Moreover, higher fluorescent antibody titer endpoints were observed with cells from static suspension cultures than with cells from spinner cultures, FL-74 cells grown in spinner culture, when subjected to partial synchrony by cold block or by deprivation of essential amino acids (arginine and/or isoleucine) for 12 hr, achieved a membrane fluorescent pattern for FOCMA similar to cells grown in static suspension. It is proposed that the expression of FOCMA on the cell membrane surface is cell-cycle dependent, and that the rate at which a cell passes through the cell cycle determines the pattern and intensity of the fluorescence of the cell membrane.

The effect of essential amino acid deprivation on macromolecular synthesis and nucleotide pool sizes in Neurospora crassa

In cultures of Neurospora crassa (leu-4, R108) deprived of an essential amino acid, there is a decrease in the amount of 32PO 4 incorporated into the 1.0 m formic acid-soluble pool, nucleotides, DNA, and RNA and a decrease in glycogen synthetase activity compared to leucine-supplemented cultures. However, energy charge values and nucleoside triphosphate to diphosphate ratios in the leucine-deprived cells approximate the values determined in exponentially growing cells. Low levels of guanosine tetraphosphate are found in both leucine-deprived and leucine-supplemented cultures. Cyclic 3′,5′-adenosine monophosphate levels were determined during exponential and prestationary phase and in leucine-deprived cultures. In leucine-supplemented cultures, an increase in the intracellular cAMP level and a decrease in the extracellular level occurs concurrently with a decrease in energy charge (from 0.78 to 0.65) occurring as exponential cultures enter prestationary phase. The energy charge (0.75) and the intracellular cAMP level in deprived cultures are comparable to values in exponentially growing cultures. However, the total cAMP produced in leucine-supplemented cultures is approximately half that produced in amino acid-deprived cultures.