Changes In Amino Acid Pool Research Articles

Tissue amino acid pool changes during the perinatal period of the rat

1. 1. Total free amino acid content in foetal liver, kidney, skin and striated muscle increases sharply during pregnancy. 2. 2. After delivery, there is no significant change in tissue total amino acid pools. 3. 3. The essential free amino acid pool in striated muscle decreases after delivery. This decrease suggests a relationship with the increased protein content in striated muscle.

Pathway of ammonium assimilation in Streptomyces venezuelae examined by amino acid analyses and 15N nuclear magnetic resonance spectroscopy.

To obtain information on the route(s) of ammonium assimilation in Streptomyces venezuelae, cell suspensions transferred to fresh medium lacking nitrogen were pulsed with [15N2]ammonium sulphate. Cells and extracellular fluids were examined by nuclear magnetic resonance and amino acid analysis to assess changes in amino acid pools and the disposition of [15N]ammonium. Following addition of [15N]ammonium, glutamate--glutamine pools of low cell density replacement cultures expanded rapidly and became progressively labelled with 15N, whereas the alanine pool size increased much more slowly and became labelled with 15N to a much lesser extent. These results are consistent with the assimilation of ammonium via glutamate dehydrogenase or glutamine synthetase--glutamate synthase rather than alanine dehydrogenase. Under anaerobic conditions, S. venezuelae assimilates ammonium into alanine rather than glutamate--glutamine. Alanine dehydrogenase may thus function as a vehicle to regenerate NAD+ to maintain substrate-level phosphorylation during periods of anaerobiosis.

Light-induced phase shifting of the circadian clock in Neurospora crassa requires ammonium salts at high pH

Effects of external ionic conditions on light induced phase shifting of the circadian rhythm of conidiation in Neurospora crassa were examined in simple buffer solutions for discerning effects of individual ions. Mycelia were cultured to liquid media of different pHs and then transferted to 10 mM piperazine-N,N'-bis(2-ethanesulmonic acid) (Pipes) buffer of various pHs and irradiated with while light. The phase of the rhythm of dark controls was not changed by transfer from medium to buffer. When mycelia were cultured in media of pH above 6.7, light did not advance the phase of the clock in Pipes buffer alone. However, light-induced phase advance was restored when an ammonium salt was added to buffer of pH higher than 7.6. An amination-defective mutant, bd am, showed the same response to ammonium nitrate as the wild-type strain, bd. Ammonium must be present before light irradiation for restoration of phase shifting. Free-amino-acid pools in the cells were changed by treatment with Pipes buffer: aspartle acid, glutamic acid, ammonia, glutamine and ornithine levels decreased, while lysine and histidine increased. Addition of ammonium nitrate to Pipes buffer resulted in further changes in amino-acid pools; lysine, histidine, arginine, alanine and ornithine decreased, and glutamine levels increased. Irradiation did not result in significant changes in amino acid pools.

RNA and protein synthetic patterns during germination of Polysphondylium pallidum microcysts.

During microcyst germination in the cellular slime mould Polysphondylium pallidum, an immediate rapid increase in the rate of protein synthesis ([3H]leucine incorporation) is observed within 15 min after the initiation of germination. The data, corrected for amino acid pool changes, reveal that the rate of protein synthesis reaches its peak at 1 1/2 h, after which it decreases. A low level of RNA synthesis ([3H]uridine incorporation) is observed after 1 h and this rate increases markedly after 2 h. Analysis of the RNA species shows a low level of synthesis of all ribosomal RNA's which begins between 1 and 2 h and increases after 2 h. The synthesis of a heterogeneously distributed, poly(A)-containing fraction of RNA (presumptive mRNA) is initiated some time after 2 h and the synthesis of a small molecular weight species in the 4-5S region is observed after 3 h. Thus, it seems that Polysphondylium microcysts show sequentially initiated synthesis of RNA during germination.

Additional Studies on the Regulation of Carbohydrate-Dependent Enzymes in the Jejunum: Changes in Amino Acid Pools, Protein Synthesis, and the Effect of Actinomycin-D.

Adaptive changes in rat jejunal disaccharidase levels during carbohydrate starvation and carbohydrate feeding were studied in relation to protein synthesis, amino acid pools, and cell migration. When animals were fed a sucrose-rich, normal protein diet for 24 hr after being on a casein-rich, carbohydrate-free diet for 7 days, there was 50% reduction in the size of the total amino acid pool without a significant change in the proportions of individual amino acids in the pool. The specific radioactivity of the leucine pool increased whenever carbohydrate was added to the diet and protein intake reduced. The incorporation of radioactive precursors into homogenate and brush border proteins reflected the characteristics of the pools, and was thus higher during carbohydrate feeding when the pool size was smaller. The rate of cell migration was unaffected by diet. Disaccharidase activities fell during prolonged carbohydrate starvation. When animals were treated with actinomycin-D, ribonucleic acid synthesis measured 18 hr later was reduced 50%, and cell migration was arrested. The drug did not inhibit the sucrose-stimulated rise in homogenate sucrase activity, although it did abolish the expected increase in fructokinase activity. With actinomycin-D treatment, brush border sucrase activity did not parallel the increases seen in the homogenate, but rather fell markedly. The data demonstrate that dietary carbohydrate increases jejunal disaccharidase activity without elevations in the rate of protein synthesis and that the effect is also independent of ribonucleic acid synthesis and cell migration. By contrast, jejunal fructokinase activity is probably regulated at the level of transcription.

Changes in amino acid pools in the rat brain following first exposure to light

Littermate rats were reared in the dark, and the free amino acid pools of visual and motor cortex regions compared in groups confined to the dark or exposed to laboratory illumination for 3 h. In the visual cortex of the dark control group, amino acid levels, in particular that of glutamate, were generally elevated compared with other regions and conditions. The effect was not due to enhanced tissue water levels. The DNA content of the experimental visual cortex was elevated in comparison with the dark control visual cortex. The significance of these observations for the study of the effects of environmental and behavioural changes on incorporation of precursors into brain proteins was discussed.

Short-term changes in amino acid pool of neurospora mycelium

Short-term changes in amino acid pool of neurospora mycelium