Levels Of Several Amino Acids Research Articles

29 PLASMA AMINO ACID LEVELS IN PRETERM INFANTS WITH BRONCHOPULMONARY DYSPLASIA ON THE FIRST DAYS OF DEXAMETHASONE TREATMENT

Plasma levels of several amino acids are increased in preterm infants after several days of treatment with dexamethasone. Acute effects, however, have not been published. We measured plasma amino acid levels immediately before (day 0), 24 hours after and 48 hours after starting treatment with dexamethasone (0.6 mg/kg/day, twice daily) in, 8 preterm infants (gestational age 26-29 weeks, birthweight 790-1485 grams) with bronchopulmonary dysplasia. Protein intake ranged from 1.1 to 2.9 g/kg/d. At 24 hours a substantial rise of nearly all amino acids was found. There was no relationship of protein intake on consecutive days or between individuals and rise in amino acid levels. Results are summarized in the table. ALA=alanine, GLU=glutamate, GLN=glutamine, LEU=leucine, ILE=isoleucine, VAL=valine, EAA=essential amino acids, TAA=total aminoacids. Data are shown as median, (range); fractional rise at 24 and 48 hours are given. CONCLUSION: These results indicate that immediately following dexamethasone treatment protein catabolism occurs, presumably by an increased breakdown of muscle protein.

Peritoneal Transport during Dialysis with Amino Acid-Based Solutions

To evaluate the potential clinical role of amino acids as an osmotic agent. The peritoneal transport of fluid, amino acids, and other solutes was investigated during a 6-hour single-cycle peritoneal dialysis with PDA 1% versus 1.36% glucose (n = 6) or PDA 2.7% versus 3.86% glucose solution (n = 9). Fifteen stable nondiabetic continuous ambulatory peritoneal dialysis (CAPD) patients. The fractional absorption of the osmotic agents at 6 hours was higher with PDA 2.7% versus glucose 3.86% (p < 0.005). The diffusive mass transport coefficient, KBD, calculated for a period of dialysate isovolemia was higher with PDA 2.7% versus PDA 1% for essential, nonessential (p < 0.005), and total (p < 0.05) amino acids. The intraperitoneal volume-over-time curves and KBD values for urea, creatinine, glucose, albumin, beta 2-microglobulin, and total protein did not differ between the amino acid solutions and the corresponding glucose solutions. KBD for urea was significantly higher during the dwell with PDA 2.7% versus PDA 1% (p < 0.05). Plasma amino acid concentrations increased substantially during the first 1-2 hours and then decreased gradually. Valine and methionine rose to 792% and 1119% of baseline values, respectively. We conclude that the peritoneal transport of fluid and investigated solutes, except amino acids, was not different with the amino acid solutions compared with the corresponding equimolar glucose solutions. However, ultrafiltration tended to be lower with amino acid solutions. Furthermore, the fractional absorption of amino acids and KBD values for amino acids was higher with PDA 2.7% versus PDA 1%, suggesting an effect of the hypertonic amino acid solution on the peritoneal membrane transport properties. Also, the hypertonic PDA 2.7% solution yielded nonphysiologically high plasma levels of several amino acids. We therefore consider this solution not to be safe enough for long-term clinical use.

Anti- Candida Activity of Cispentacin: The Active Transport by Amino Acid Permeases and Possible Mechanisms of Action

Cispentacin transport into Candida albicans CCH442 was via a specific inducible proline permease and other amino acid permeases. Drug entry was also dependent upon the proton motive force. The apparent K m and V max for drug uptake under induced conditions were 0.4 mM and 7 nmol/μl/min, respectively, with cellular accumulation in the mM range. Cispentacin uptake was competitively inhibited by L-proline with an apparent K i of 75 μM. Cispentacin did not charge to transfer-RNA or incorporate into protein; however, the compound did inhibit in vivo incorporation of [ 14C]lysine into protein and [ 3H]adenine into RNA as well as in vitro [ 14C]proline charging to transfer-RNA. Cispentacin did not inhibit amino acid biosynthesis in vivo but did elevate levels of several amino acids possibly by interfering with self-regulatory mechanisms.

Astrocyte heterogeneity: endogenous amino acid levels and release evoked by non-N-methyl-D-aspartate receptor agonists and by potassium-induced swelling in type-1 and type-2 astrocytes.

The aim of the present study was to determine whether endogenous amino acids are released from type-1 and type-2 astrocytes following non-N-methyl-D-aspartate (NMDA) receptor activation and whether such release is related to cell swelling. Amino acid levels and release were measured by HPLC in secondary cultures from neonatal rat cortex, highly enriched in type-1 or type-2 astrocytes. The following observations were made. (a) The endogenous level of several amino acids (glutamate, alanine, glutamine, asparagine, taurine, serine, and threonine) was substantially higher in type-1 than in type-2 astrocytes. (b) The spontaneous release of glutamine and taurine was higher in type-1 than in type-2 astrocytes; that of other amino acids was similar. (c) Exposure of type-2 astrocyte cultures to 50 microM kainate or quisqualate doubled the release of glutamate and caused a lower, but significant increase in that of aspartate, glycine, taurine, alanine, serine (only in the case of kainate), and glutamine (only in the case of quisqualate). These effects were reversed by the antagonist CNQX. (d) Exposure of type-1 astrocyte cultures to 50-200 microM kainate or 50 microM quisqualate did not affect endogenous amino acid release, even after treating the cultures with dibutyryl cyclic AMP. (e) Exposure of type-1 or type-2 astrocyte cultures to 50 mM KCl (replacing an equimolar concentration of NaCl) enhanced the release of taurine greater than glutamate greater than aspartate. The effect was somewhat more pronounced in type-2 than in type-1 astrocytes. Veratridine (50 microM) did not cause any increase in amino acid release. (f) The release of amino acids induced by high [K+] appeared to be related to cell swelling, in both type-1 and type-2 astrocytes. Swelling and K(+)-induced release were somewhat higher in type-2 than in type-1 astrocytes. In contrast, neither kainate nor quisqualate caused any appreciable increase in cell volume. It is concluded that non-NMDA receptor agonists stimulate the release of several endogenous amino acids (some of which are neuroactive) from type-2 but not from type-1 astrocytes. The effect does not seem to be related to cell swelling, which causes a different release profile in both type-1 and type-2 astrocytes. The absence of kainate- and quisqualate-evoked release in type-1 astrocytes suggests that the density of non-NMDA receptors in this cell type is very low.

Oral absorption of biologically active insulin in common carp ( Cyprinus carpio L.)

1. 1. Bovine insulin dissolved in 0.05 M deoxycholic acid was absorbed through oral intubation in fish weighing 200–300 g. 2. 2. The peak of absorption appeared in all fish, 30–45 min after intubation and was followed by a gradual decrease. The extent of absorption was extremely variable, with up to a 20-fold difference between individuals. No detectable insulin was found in fish intubated with vehicle. 3. 3. The absorbed hormone retained 17–88% of its lipogenic bioaetivity in vitro. The absorbed insulin lowered the levels of several amino acids in the intubated fish, indirectly indicating that its bioactivity was also retained in vivo.

Effect of acetyl‐L‐carnitine on the dopaminergic system in aging brain

We studied the effect of acetyl-L-carnitine (ALCAR) on dopamine release and the effect of long-term acetyl-L-carnitine treatment on age-related changes in striatal dopamine receptors and brain amino acid levels. In striatal tissue that had been incubated with [3H]dopamine, acetyl-L-carnitine increased the release of [3H]dopamine evoked by electrical stimulation. In striatal tissue from aged mice administered acetyl-L-carnitine for 3 months, the release of [3H]dopamine evoked by electrical stimulation was higher than that of its aged control; the release after a second stimulation was similar in the two groups. There was a significant decline in the number of D1 striatal dopamine receptors with age. The Bmax was 51% lower in 1.5-year-old mice than in 4-month-old animals. Administration of acetyl-L-carnitine for 3 months diminished the reduction in the binding of [3H]SCH-23390. [3H]Spiperone binding to D2 receptors was not decreased with age and was not affected by acetyl-L-carnitine treatment. Age-related decreases in levels of several amino acids were observed in several brain regions. Acetyl-L-carnitine lessened the reduction in the level of taurine only in the striatum. The findings confirm the multiple effects of acetyl-L-carnitine in brain, and suggest that its administration can have a positive effect on age-related changes in the dopaminergic system.

Biochemical response of Norway spruce ( Picea abies (L.) Karst.) towards 14-month exposure to ozone and acid mist: Effects on amino acid, glutathione and polyamine titers

Two clones of Norway spruce were exposed to elevated ozone levels (100 μg m −3 with episodes of 130–360 μg m −3) in combination with acidic mist (pH 3·0) for two vegetation periods. The plants did not exhibit any visible injury, but levels of several amino acids and polyamines were altered in comparison with control plants (50 μg m −3 ozone, mist of pH 5·6), the changes being pronounced in clone 14. Total free amino acids as well as methionine titers were increased in clone 14. Asparagine was significantly increased in clone 11 and less so in clone 14. Arginine, which comprised more than 50% of the free amino acids in spruce needles, was not changed by the exposure regime applied. Reduced glutathione was significantly increased in all clones/soil/needle age combinations (average increase 50%). Free soluble putrescine was enhanced by 50–200% in clone 14, but remained unchanged in clone 11. Conjugated putrescine was significantly, and conjugated spermidime was slightly, increased in both clones, whereas other polyamines did not responde to the treatment.

In vitro effect of caffeine on some aspects of nitrogen metabolism in isolated rat hepatocytes

Long-term exposure to high doses of caffeine affects several aspects of nitrogen metabolism, such as purine, pyrimidine and urea synthesis. However, little is known about the mechanisms of these changes and if they occur at shorter term. We have studied in isolated hepatocytes: 1) the in vitro effect of high doses of caffeine on amino acid levels, 2) the main destination of ammonia and carbon chains from amino acid catabolism, and 3) the cytosolic and mitochondrial redox states. We have found that, whereas it has a small effect on urea synthesis and on the levels of the cofactors and intermediates, it decreases the levels of several amino acids, the gluconeogenesis and the redox state. Our results suggest that a longer exposure to caffeine is necessary to affect the normal functions of some metabolic pathways.

Carbohydrate ingestion and brain serotonin synthesis: Relevance to a putative control loop for regulating carbohydrate ingestion, and effects of aspartame consumption

The ingestion of a meal of carbohydrates by fasting rats rapidly increases brain tryptophan level and serotonin (5-HT) synthesis. The rise in brain tryptophan level follows from an increase in tryptophan transport into brain, the consequence of an insulin-induced reduction in the blood levels of several amino acids that compete with tryptophan for brain uptake. In contrast, ingesting protein with carbohydrate does not stimulate brain tryptophan uptake or 5-HT synthesis, because the blood levels of tryptophan's transport competitors are increased, not reduced. These observations form the biochemical basis of a current proposal for a regulatory loop governing meal-to-meal appetite for carbohydrates. This review briefly analyzes the experimental basis for the carbohydrate appetite regulatory loop, and finds it wanting. It also considers the proposal that the ingestion of the artificial sweetener aspartame might disrupt the putative regulatory loop for carbohydrate intake regulation, and thus promote rather than help to limit carbohydrate appetite, and finds this hypothesis unrealistic as well. In general, the conclusion is that while single meals do readily influence brain tryptophan uptake and 5-HT synthesis, it is presently unclear what role such neurochemical effects of food ingestion have in the control of specific appetites.

Evaluation of the effect of arginine-enriched amino acid solution on tumor growth.

To investigate the effect of arginine-enriched solution on tumor growth and metastasis, rats were infused with solutions containing 5.5 and 0.66% arginine for 8 days. Infusions were started at the same time of subcutaneous transplant of Yoshida sarcoma. Arginine-rich solution suppressed tumor growth at an early stage and prevented metastases to the liver and kidney. In addition, arginine supplements enhanced the phagocytic activity of alveolar macrophages. It also resulted in maintenance of a positive nitrogen balance and prevented the increases in the levels of several amino acids observed in the control group. The suppressive effect of arginine-enriched solution on tumor growth may be due to its activation of the immunologic system, in which the phagocytic activity of macrophages probably participates.

Influence of caecectomy and source of dietary fibre or starch on excretion of endogenous amino acids by laying hens

Two experiments were conducted to evaluate the effects of caecectomy and source of dietary fibre and starch on excretion of amino acids by laying hens. In Expt 1, caecectomized hens excreted significantly higher levels of several amino acids than intact hens during a 24 h fasting period. These differences were greatest for threonine, proline and leucine. In Expt 2, caecectomized and intact hens were given either a nitrogen-free diet containing 500 g cellulose/kg or one containing 400 g uncooked potato starch/kg and 100 g citrus pectin/kg. The potato starch-pectin (PSP) diet increased excretion of most amino acids by both caecectomized and intact hens compared with the cellulose diet, with this response being larger for intact hens. When compared across diets, caecectomized hens excreted more threonine and serine than intact hens. Excreta voided by hens given PSP contained higher levels of alanine and valine and lower levels of aspartic acid, glutamic acid and methionine than excreta from the cellulose diet. When compared across diets, excreta from caecectomized hens contained more threonine, serine and isoleucine and less aspartic acid and alanine than excreta from intact hens. Multiple regression analyses of excreta amino acid profiles on profiles of endogenous and microbial protein suggested that the intestinal microflora had greater influence on amino acids excreted by caecectomized hens than on those excreted by intact hens.

Kinetics and metabolic effects of orally administered ornithine α-ketoglutarate in healthy subjects fed with a standardized regimen

In accordance with previous results obtained with traumatized patients, ornithine α-ketoglutarate (OKG) was orally administered to 10 healthy subjects fed with a standardized regimen. Six similarly fed control subjects received only water. Plasma and 24-h urinary amino acids and α-ketoglutarate, plasma glucose, plasma insulin, and urine urea were all measured. After administration of ornithine α-ketoglutarate, the rapid decrease in blood ornithine to basal values, the absence of any increase in plasma α-ketoglutarate levels, and the minimal increase in ornithine, α-ketoglutarate, and urea urinary elimination, all indicated intense metabolism and utilization of the two compounds. These results suggest that the hyperornithinemia observed in 4-h fasting, traumatized patients receiving ornithine α-ketoglutarate reflects a metabolic perturbation in the utilization of this amino acid after trauma, rather than a hypothetical slow utilization. On the other hand, ornithine α-ketoglutarate induced an increase in insulin levels causing hypoglycemia and probably a decrease in plasma levels of several amino acids.

Measurement of intracellular amino acids in cultured fibroblasts

Tissue culture is a valuable tool for the study of cellular amino acid metabolism. However, accurate measurement of intracellular amino acids is difficult. Cells must be washed to remove the culture medium which is rich in amino acids, a procedure which may result in the loss of intracellular amino acids. Collection of the cells for washing and amino acid measurement is further complicated by the adherence of cultured fibroblasts to the culture vessel surface. An uncomplicated, reliable method for the determination of the amino acid content of cultured human diploid fibroblasts is described. The intracellular levels of several amino acids determined by this method are markedly higher than previously reported levels.

Influence of branched‐chain amino acid infusion on arterial concentrations and brain exchange of amino acids in patients with hepatic cirrhosis

Summary. The influence of branched‐chain amino acid (BCAA) infusion on arterial concentrations and brain exchange of amino acids was studied in seven patients with hepatic cirrhosis and in six healthy control subjects. Arterial levels and arterial‐jugular venous (A‐JV) concentration differences for amino acids, glucose, ketone bodies and lactate were measured in the basal state and during a constant rate, 150 min intravenous infusion of a BCAA solution (250 fmiol/min, 70% L‐leucine, 20% L‐valine and 10% L‐isoleucine). In the basal state the arterial whole blood concentrations of tyrosine, phenylalanine and methionine were 40–130 % higher in the cirrhotic patients compared to the controls, while the levels of the BCAA were 20–35 % lower. The patients' concentration of aspartic acid was 70% below the corresponding control value. During BCAA infusion the arterial leucine concentration rose 4–5 fold while valine increased 60–95% and isoleucine rose 45–50%. The arterial levels of several amino acids decreased progressively in a similar manner in patients and controls. At the end of the 150 min infusion period methionine had decreased 35% (P&lt;001), tyrosine 25% (P&lt;0–001) and phenylalanine 35% (P&lt;0–001) in the patient group. Positive A‐JV differences in amino acid concentration–indicating net brain uptake–were seen for leucine, isoleucine, valine, serine, tyrosine and lysine in both groups in the basal state. The patients had a greater A‐JV difference than the controls for tyrosine (P&lt;0–05) while the uptake of the other amino acids, including the BCAA, was similar in the two groups. The fractional uptake of leucine and valine was significantly increased in the patients. During BCAA infusion the A‐JV difference for leucine increased 2–3 fold in both patients and controls and the net uptake to the brain of tyrosine and phenylalanine was abolished in the patient group. It is concluded that (a) patients with hepatic cirrhosis show a decreased whole blood concentration of aspartate indicating a reduced intracellular concentration of this amino acid, (b) brain uptake of tyrosine and fractional uptake of leucine and valine is augmented in patients with hepatic cirrhosis, demonstrating abnormal brain amino acid uptake in this disorder, and (c) BCAA infusion effectively lowers the arterial concentrations for tyrosine, phenylalanine and methionine in cirrhotic patients as well as in healthy controls and blocks the abnormal brain uptake of tyrosine. These findings provide a biochemical background to the suggested beneficial effect of BCAA infusion in patients with hepatic cirrhosis and portal systemic encephalopathy.

Amino acid solutions: composition and suitability for intravenous feeding in infants.

The amino acid composition, the electrolyte content, the titratable acidity, the osmolality and the pH of nine crystalline amino acid mixtures and one protein hydrolysate was analyzed and the results were compared with the data provided by the manufacturer. The amino acid composition of the protein hydrolysate (Aminosol 10%) showed a marked discrepancy between the concentration of amino acids measured and the concentration given by the manufacturer. The sodium, chloride and especially the ammonia content is high as compared to the synthetic amino acid solutions. The amino acid composition of the crystalline amino acid solutions was generally in reasonable good agreement with the composition given by the manufacturers. In DL-Trophysan an unknown amino acid, probably alloisoleucine, was found. Only in two (Vamin 7% and Amino acid solution 4200) out of eleven crystalline amino acid mixtures cystine and tyrosine could be detected; therefore only Amino acid solution 4200 and Vamin 7% might be suited for infants. However, infants fed parenterally with Vamin 7% often showed elevated levels of several amino acids. Amino acid solution 4200 with a composition similar to human milk seems to be more adapted and needs further investigation.

Reduction of ribosome activity and synthesis of stable RNA in Neurospora crassa

The addition of cycloheximide (0.02 μg/ml) to exponentially growing cultures of Neurospora crassa causes a reduction in growth rate and a decrease in the rate of protein accumulation, due to a partial inhibition of protein synthesis, while RNA accumulation is unaffected for about 1 h. Thus, an increased RNA: protein ratio is established in the presence of the inhibitor. RNA that accumulates during treatment with cycloheximide has the same characteristics as that of the control cultures and this, together with the enhancement of the relative rate of synthesis of ribosomal proteins induced by cycloheximide, seems to indicate that more mature ribosomes are present in cycloheximide-treated cultures. The endocellular level of several amino acids begins to increase significantly only 60 min after cycloheximide addition. A possible explanation of the stimulation of ribosome production induced by cycloheximide is given in terms of the existence of a feed-back mechanism controlling ribosome synthesis.

Levels of several amino acids in the cerebellar peduncles and four medullary nuclei of control and 3-acetylpyridine-treated rats.

The levels of aspartate, glutamate, GABA, taurine, glycine, and alanine were determined in the inferior (ICP), middle (MCP) and superior (SCP) cerebellar peduncles, and in the inferior olive (ION), lateral reticular (LRN), lateral vestibular (LVN) and descending trigeminal (DTN) nuclei of control rats and of rats given a single intraperitoneal injection of 65 mg/kg of 3-acetylpyridine (3-AP). The content of glutamate in the MCP and SCP was 30% higher than that found for the ICP. The content of GABA was 4 to 6-fold greater in the SCP than in either the ICP or MCP. The level of taurine in the SCP was 25% lower than the value in the MCP but was not significantly lower than the value for the ICP. The levels of aspartate, glycine, and alanine were evenly distributed among the three peduncles. The contents of aspartate, glutamate, taurine, and alanine were evenly distributed among the four medullary nuclei. The level of glycine was significantly greater in the DTN than in either the LRN or LVN. The content of GABA in the ION and LVN was significantly greater than the value found for the LRN. Injection of 3-AP caused a decrease in the level of taurine of 10% in the ION and LRN, 15% in the LVN, and 25% in the DTN. No other statistically significant differences were found in the levels of the amino acids in the peduncles or medullary nuclei following 3-AP treatment. The present data do not support the idea that asparate and/or taurine are present in relatively high concentrations in the cerebellar climbing fibers.

The Thrombogenicity of 6-Azauridine

The antimetabolite 6-azauridine blocks the de novo synthesis of pyrimidines and causes increased serum levels of several amino acids including homocystine. 6-Azauridine was was withdrawn from clinical use for the treatment of psoriasis because of the occurence of arterial and venous thromboembolic episodes in some psoriatic patients. Utilizing a standard animal model for the recognition of venous and arterial thrombosis, 6-azauridine was demonstrated in this study to cause thrombosis without producing homocystinemia when administered orally or intravenously.

Effects of 3-acetylpyridine on the levels of several amino acids in different CNS regions of the rat.

The effects of one intraperitoneal injection of 60–65 mg/kg of 3-acetylpyridine (3-AP) on the levels of aspartate, glutamate, GABA, taurine, glycine, and alanine in the cerebellum, medulla, telencephalon, and diencephalon-mesencephalon of the rat were studied at various times (4–28 days) after injection. In the first 4–7 days, the levels of glutamate, GABA, glycine, and alanine in the cerebellum were 10–30% higher in the 3-AP-treated rats than in the control animals. By day 14, the levels of these four amino acids were normal (in the case of glutamate and glycine) or below normal (for GABA and alanine). By day 21, the values for GABA and alanine returned to normal. In the first 7 days, the level of aspartate in the cerebellum was the same in both the 3-AP- and saline-injected groups. From days 14 to 28, the level of aspartate in the cerebellum was 10–20% lower in the 3-AP-injected group than in the saline-treated animals. The level of taurine in the cerebellum was 15–30% lower in the 3-AP group than in the control group from days 7 to 28. The pattern of changes observed in the medulla in the first 7 days was similar to that found in the cerebellum for this period. However, unlike the data for the cerebellum, the level of aspartate in the medulla was unchanged by the 3-AP injection from day 14 to day 28, and the level of glutamate in the medulla remained higher (10–15%) from days 14 to 28 in the 3-AP-injected animals with respect to control values. The levels of taurine in the medulla were lower (10–15%) from day 7 to day 28 in the 3-AP injected group with respect to control values. The injection of 3-AP did not alter the levels of aspartate, glutamate, GABA, taurine, glycine, or alanine in the telencephalon on days 7, 14, 21, or 28 and in the diencephalon-mesencephalon on day 21 with respect to control levels.

PREPARATION AND STORAGE OF SWEET POTATO FLAKES FORTIFIED WITH PLANT PROTEIN CONCENTRATES AND ISOLATES

ABSTRACTSweet potato flakes supplemented with soy flour, soy flour plus DL‐methionine, cottonseed flour and wheat gluten flour were prepared. The fortified flakes had higher protein calorie to total calorie ratios but had lower water‐binding capacity than flakes with no supplementary material. The amino acid pattern of soy flour, soy plus methionine and cottonseed flour formulations compared favorably with that of non‐supplemented flakes. Each formulation was stored at 23° and 40°C under nitrogen for 8.25 months. Although the levels of several amino acids appeared to change significantly during storage, only glycine in the gluten formulation linearly decreased. Tyrosine in the soy formulation appeared to increase during storage. Flakes stored at 40°C appeared to develop off flavors and to lose water‐binding capacity.