Association Between Early Amino Acid Intake and Full-Scale IQ at Age 5 Years Among Infants Born at Less Than 30 Weeks' Gestation

IMPORTANCE

An international expert committee recently revised its recommendations on amino acid intake for very preterm infants, suggesting that more than 3.50 g/kg/d should be administered only to preterm infants in clinical trials. However, the optimal amino acid intake during the first week after birth in these infants is unknown.

OBJECTIVE

To evaluate the association between early amino acid intake and cognitive outcomes at age 5 years.

DESIGN, SETTING, AND PARTICIPANTS

Using the EPIPAGE-2 (Epidemiologic Study on Small-for-Gestational-Age Children-Follow-up at Five and a Half Years) cohort, a nationwide prospective population-based cohort study conducted at 63 neonatal intensive care units in France, a propensity score-matched analysis was performed comparing infants born at less than 30 weeks' gestation who had high amino acid intake (3.51-4.50 g/kg/d) at 7 days after birth with infants who did not. Participants were recruited between April 1 and December 31, 2011, and followed up from September 1, 2016, to December 31, 2017. Full-scale IQ (FSIQ) was assessed at age 5 years. A confirmatory analysis used neonatal intensive care unit preference for high early amino acid intake as an instrumental variable to account for unmeasured confounding. Statistical analysis was performed from January 15 to May 15, 2021.

EXPOSURES

Amino acid intake at 7 days after birth.

MAIN OUTCOMES AND MEASURES

The primary outcome was an FSIQ score greater than -1 SD (ie, ≥93 points) at age 5 years. A complementary analysis was performed to explore the association between amino acid intake at day 7 as a continuous variable and FSIQ score at age 5 years. Data from cerebral magnetic resonance imaging at term were available for a subgroup of preterm infants who participated in the EPIRMEX (Cerebral Abnormalities Detected by MRI, Realized at the Age of Term and the Emergence of Executive Functions) ancillary study.

RESULTS

Among 1789 preterm infants (929 boys [51.9%]; mean [SD] gestational age, 27.17 [1.50] weeks) with data available to determine exposure to amino acid intake of 3.51 to 4.50 g/kg/d at 7 days after birth, 938 infants were exposed, and 851 infants were not; 717 infants from each group could be paired. The primary outcome was known in 396 of 646 exposed infants and 379 of 644 nonexposed infants who were alive at age 5 years and was observed more frequently among exposed vs nonexposed infants (243 infants [61.4%] vs 206 infants [54.4%], respectively; odds ratio [OR], 1.33 [95% CI, 1.00-1.71]; absolute risk increase in events [ie, the likelihood of having an FSIQ score >-1 SD at age 5 years] per 100 infants, 7.01 [95% CI, 0.06-13.87]; P = .048). In the matched cohort, correlation was found between amino acid intake per 1.00 g/kg/d at day 7 and FSIQ score at age 5 years (n = 775; β = 2.43 per 1-point increase in FSIQ; 95% CI, 0.27-4.59; P = .03), white matter area (n = 134; β = 144 per mm2; 95% CI, 3-285 per mm2; P = .045), anisotropy of the corpus callosum (n = 50; β = 0.018; 95% CI, 0.016-0.021; P < .001), left superior longitudinal fasciculus (n = 42; β = 0.018; 95% CI, 0.010-0.025; P < .001), and right superior longitudinal fasciculus (n = 42; β = 0.014 [95% CI, 0.005-0.024; P = .003) based on magnetic resonance imaging at term. Confirmatory and sensitivity analyses confirmed these results. For example, the adjusted OR for the association between the exposure and the primary outcome was 1.30 (95% CI, 1.16-1.46) using the instrumental variable approach among 978 participants in the overall cohort, and the adjusted OR was 1.35 (95% CI, 1.05-1.75) using multiple imputations among 1290 participants in the matched cohort.

CONCLUSIONS AND RELEVANCE

In this cohort study, high amino acid intake at 7 days after birth was associated with an increased likelihood of an FSIQ score greater than -1 SD at age 5 years. Well-designed randomized studies with long-term follow-up are needed to confirm the benefit of this nutritional approach.

Need for speed: evaluation of dilute and shoot-mass spectrometry for accelerated metabolic phenotyping in bioprocess development

With the utilization of small-scale and highly parallelized cultivation platforms embedded in laboratory robotics, microbial phenotyping and bioprocess development have been substantially accelerated, thus generating a bottleneck in bioanalytical bioprocess sample analytics. While microscale cultivation platforms allow the monitoring of typical process parameters, only limited information about product and by-product formation is provided without comprehensive analytics. The use of liquid chromatography mass spectrometry can provide such a comprehensive and quantitative insight, but is often limited by analysis runtime and throughput. In this study, we developed and evaluated six methods for amino acid quantification based on two strong cation exchanger columns and a dilute and shoot approach in hyphenation with either a triple-quadrupole or a quadrupole time-of-flight mass spectrometer. Isotope dilution mass spectrometry with 13C15N labeled amino acids was used to correct for matrix effects. The versatility of the methods for metabolite profiling studies of microbial cultivation supernatants is confirmed by a detailed method validation study. The methods using chromatography columns showed a linear range of approx. 4 orders of magnitude, sufficient response factors, and low quantification limits (7-443 nM) for single analytes. Overall, relative standard deviation was comparable for all analytes, with < 8% and < 11% for unbuffered and buffered media, respectively. The dilute and shoot methods with an analysis time of 1 min provided similar performance but showed a factor of up to 35 times higher throughput. The performance and applicability of the dilute and shoot method are demonstrated using a library of Corynebacterium glutamicum strains producing L-histidine, obtained from random mutagenesis, which were cultivated in a microscale cultivation platform.

Determination of purity values of amino acid reference materials by mass balance method: an approach to the quantification of related structure impurities

A systematic procedure for the determination of purity values of amino acid reference materials was developed by use of mass balance method where four categories of impurities (related structure impurities (RSIs), water, organic solvent residue (OSR), and non-volatile residue (NVR)) were quantified separately. The amount of RSIs was determined using a combination of three quantification methods. To ensure metrological traceability in the determination of RSIs, at least one such impurity in each candidate amino acid reference material was quantified using liquid chromatography-isotope dilution tandem mass spectrometry (LC-IDMS/MS). Other RSIs were determined using external calibration liquid chromatography-tandem mass spectrometry (LC-MS/MS) or o-phthaldialdehyde (OPA) derivatization, followed by liquid chromatography-ultraviolet (LC-UV) measurement. As the UV absorption of most RSIs came basically from the same chromophore after OPA derivatization, a relative peak area approach was used in the LC-UV method to quantify the amount of RSIs by comparing their peak areas with that of a reference RSI. The reference RSI was pre-selected and the amount determined by LC-IDMS/MS separately. The absence of D-amino acids was confirmed using Marfey's reagent derivatization, followed by LC-UV analysis. The amounts of water, OSR, and NVR were measured using Karl Fischer coulometry, gas chromatography-mass spectrometry (GC-MS) and thermogravimetry, respectively. By using this procedure, four amino acid (L-valine, L-leucine, L-isoleucine, and L-phenylalanine) certified reference materials (CRMs) were developed from the candidate materials. The homogeneity and stability of the CRMs were demonstrated by use of LC-IDMS/MS or OPA-LC-UV method, following the principles in ISO 17034 and ISO Guide 35.Graphical abstract.

Fusing metabolomics data sets with heterogeneous measurement errors

Combining different metabolomics platforms can contribute significantly to the discovery of complementary processes expressed under different conditions. However, analysing the fused data might be hampered by the difference in their quality. In metabolomics data, one often observes that measurement errors increase with increasing measurement level and that different platforms have different measurement error variance. In this paper we compare three different approaches to correct for the measurement error heterogeneity, by transformation of the raw data, by weighted filtering before modelling and by a modelling approach using a weighted sum of residuals. For an illustration of these different approaches we analyse data from healthy obese and diabetic obese individuals, obtained from two metabolomics platforms. Concluding, the filtering and modelling approaches that both estimate a model of the measurement error did not outperform the data transformation approaches for this application. This is probably due to the limited difference in measurement error and the fact that estimation of measurement error models is unstable due to the small number of repeats available. A transformation of the data improves the classification of the two groups.

Calcium Chloride and Calcium Gluconate in Neonatal Parenteral Nutrition Solutions without Cysteine: Compatibility Studies Using Laser Light Obscuration Methodology

There are no compatibility studies for neonatal parenteral nutrition solutions without cysteine containing calcium chloride or calcium gluconate using light obscuration as recommended by the United States Pharmacopeia (USP). The purpose of this study was to do compatibility testing for solutions containing calcium chloride and calcium gluconate without cysteine. Solutions of TrophAmine and Premasol (2.5% amino acids), containing calcium chloride or calcium gluconate were compounded without cysteine. Solutions were analyzed for particle counts using light obscuration. Maximum concentrations tested were 15 mmol/L of calcium and 12.5 mmol/L of phosphate. If the average particle count of three replicates exceeded USP guidelines, the solution was determined to be incompatible. This study found that 12.5 and 10 mmol/L of calcium and phosphate, respectively, are compatible in neonatal parenteral nutrition solutions compounded with 2.5% amino acids of either TrophAmine or Premasol. There did not appear to be significant differences in compatibility for solutions containing TrophAmine or Premasol when solutions were compounded with either CaCl₂ or CaGlu-Pl. This study presents data in order to evaluate options for adding calcium and phosphate to neonatal parenteral nutrition solutions during shortages of calcium and cysteine.

Investigation of the effects of storage and freezing on mixes of heavy-labeled metabolite and amino acid standards

RATIONALE

High-throughput metabolomics has now made it possible for small/medium-sized laboratories to analyze thousands of samples/year from the most diverse biological matrices including biofluids, cell and tissue extracts. In large-scale metabolomics studies, stable-isotope-labeled standards are increasingly used to normalize for matrix effects and control for technical reproducibility (e.g. extraction efficiency, chromatographic retention times and mass spectrometry signal stability). However, it is currently unknown how stable mixes of commercially available standards are following repeated freeze/thaw cycles or prolonged storage of aliquots.

METHODS

Standard mixes for ¹³ C, ¹⁵ N or deuterated isotopologues of amino acids and key metabolites from the central carbon and nitrogen pathways (e.g. glycolysis, Krebs cycle, redox homeostasis, purines) were either repeatedly frozen/thawed for up to 10 cycles or diluted into aliquots prior to frozen storage for up to 42 days. Samples were characterized by ultra-high-pressure liquid chromatography/mass spectrometry to determine the stability of the aliquoted standards upon freezing/thawing or prolonged storage.

RESULTS

Metabolite standards were stable over up to 10 freeze/thaw cycles, with the exception of adenosine and glutathione, showing technical variability across aliquots in a freeze/thaw-cycle-independent fashion. Storage for up to 42 days of mixes of commercially available standards did not significantly affect the stability of amino acid or metabolite standards for the first 2 weeks, while progressive degradation (statistically significant for fumarate) was observed after 3 weeks.

CONCLUSIONS

Refrigerated or frozen preservation for at least 2 weeks of aliquoted heavy-labeled standard mixes for metabolomics analysis is a feasible and time-/resource-saving strategy for standard metabolomics laboratories.

Amphiphilic erythromycin-lipoamino acid ion pairs: characterization and in vitro microbiological evaluation

A series of amphiphilic ion pairs of erythromycin (ERY) with lipoamino acids (LAAs) were produced. The ion pairs were prepared by evaporation of a water/ethanol co-solution of the drug and LAA bearing an alkyl side chain of 10-16 carbon atoms. For the sake of comparison, equimolar physical mixtures were prepared by triturating ERY and the LAA in the absence of any solvent. FTIR spectroscopy confirmed the structure of ion pairs, while differential scanning calorimetry and powder X-ray diffractometry were used to assess the formation of new saline species. The solubility pattern of the coevaporates in different aqueous and organic solvents confirmed their amphiphilic properties. ERY-LAA ion pairs were submitted to an in vitro microbiological assay against different bacterial strains, both susceptible and resistant to macrolides. The presence of the LAA moiety was shown not altering the antibacterial spectrum of activity of the drug. These results can be the basis for a further evaluation of ERY-LAA ion pairs as a mean to improve the penetration of the drug inside bacterial cells and to optimize the loading of ERY in lipid-based nanocarriers.

Analysis of Neuroactive Amines in Fermented Beverages Using a Portable Microchip Capillary Electrophoresis System

A portable microfabricated capillary electrophoresis (CE) instrument is used for the determination of neurologically active biogenic amines, especially tyramine and histamine, in fermented beverages. The target molecules are labeled on their primary amino groups with fluorescamine in a 10-min reaction, and the samples analyzed directly, producing a detailed electropherogram in only 120 s on a microfabricated glass CE device containing 21.4-cm-long separation channels. Tyramine was found mainly in red wines at <1-3.4 mg/L, while the histamine content of these samples ranged from 1.8 to 19 mg/L. The highest levels of histamine (20-40 mg/L) were found in sake. The analysis of samples drawn from grape crush through malolactic fermentation in four varieties of zinfandel red wines revealed that histamine and tyramine are produced during yeast and malolactic fermentation, respectively. Following malolactic fermentation, the histamine content in these samples ranged from 3.3 to 30 mg/L, and the tyramine content ranged from 1.0 to 3.0 mg/L. This highly sensitive and rapid lab-on-a-chip analysis method establishes the feasibility of monitoring neurologically active amine content and potentially other chemically and allergenically important molecules in our food supply.

Amino acids: Aspects of impurity profiling by means of CE

Quality control of active pharmaceutical ingredients (API) is commonly performed by means of HPLC. However, CE offers a suitable alternative, especially for the analysis of easily chargeable substances, i.e., amino acids. The article reviews, on the one hand, CE methods developed for impurity profiling of synthesized amino acid analogs. However, nowadays, production of amino acids/peptides is dominated by fermentation. Therefore, on the other hand, CE methods for the analysis of amino acids and small peptides are reported. The results of CE analysis of glutathione samples according to the monograph in the European Pharmacopoeia (Ph. Eur.) 5.7 and amino acid samples after derivatization with 9-fluorenylmethyl chloroformate (FMOC) and 3-(4-carboxybenzoyl)quinoline-2-carboxaldehyde (CBQCA) may pave the way for impurity profiling of fermentatively produced API by means of CE.

Assessment of implementation of a standardized parenteral formulation for early nutritional support of very preterm infants

INTRODUCTION

Parenteral nutrition (PN) plays an important role in the nutritional support of very preterm newborns. It has been suggested that a high proportion of PN orders could be standardized. In 2002, we implemented in our unit the preparation of three standardized formulations for PN adapted to the nutritional requirements of premature infants<32 weeks. Following this change of practice, a retrospective observational study was conducted to evaluate the relevance of the implemented standardized PN regime. Twenty premature inborn infants<32 weeks gestation who had received standardized (STD) PN in 2003 were matched for 20 infants who had received individualized (IND) PN in 2001. Adequacy of nutrition was assessed by comparing daily intravenous nutrient intake and biochemical parameters during the first week. Amino-acid intakes on day 3 were higher in the STD group (1.5+/-0.2 g/kg/d vs. 0.9+/-0.5, p<0.001), and the calcium phosphate intakes were better balanced. The cumulated intake of amino acids for the first week was greater in the STD group (+20% ; p=0.0003). Biochemical parameters were similar in both groups. Insulin infusions were less frequent in the STD group (p<0.06).

CONCLUSION

Standardized parenteral formulations provided higher early intakes of amino acid and glucose, a better calcium phosphate ratio, and a greater amount of amino-acid intakes during the first week while maintaining the same biochemical parameters. This strategy forms part of an approach concerning quality control and the respect of good professional practice for the preparation of parenteral nutrition solutions.

Content and quality of protein in proso millet (Panicum miliaceum L.) varieties

Proso millet belongs to the oldest cereals that human is using. Eight varieties of proso millet were cultivated in Ceske Budejovice from 1998 to 2000 and Cerveny Dvur from 1999 to 2000. The crude protein content was determined according to Kjehladl method and amino acid content was determined chromatographically after acid and oxidative acid hydrolysis. Although the protein content of proso (11.6% of dry matter) was similar to wheat, the grain of proso was significant richer in essential amino acids (leucine, isoleucine, methionine) then wheat. Hence, the protein quality of proso (Essential Amino Acid Index) was higher (51%) compared to wheat. The proso grain contained about 3.3 g kg(-1) of the limiting amino acid-lysine. Significant differences in protein and its quality were found among the evaluated proso varieties. The varieties Toldanskoe and Lipetskoe were the most different from the others in protein and amino acid content and Amino Acid Score of individual acids. They had the lowest content and quality of protein. The seed coat of these varieties was red. The amino acid and protein content was significantly influenced by weather during the year. Dry conditions caused an increase of protein but its quality was decreased.

Amino acid distribution in meteorites: diagenesis, extraction methods, and standard metrics in the search for extraterrestrial biosignatures

The relative abundance of the protein amino acids has been previously investigated as a potential marker for biogenicity in meteoritic samples. However, these investigations were executed without a quantitative metric to evaluate distribution variations, and they did not account for the possibility of interdisciplinary systematic error arising from inter-laboratory differences in extraction and detection techniques. Principal component analysis (PCA), hierarchical cluster analysis (HCA), and stochastic probabilistic artificial neural networks (ANNs) were used to compare the distributions for nine protein amino acids previously reported for the Murchison carbonaceous chondrite, Mars meteorites (ALH84001, Nakhla, and EETA79001), prebiotic synthesis experiments, and terrestrial biota and sediments. These techniques allowed us (1) to identify a shift in terrestrial amino acid distributions secondary to diagenesis; (2) to detect differences in terrestrial distributions that may be systematic differences between extraction and analysis techniques in biological and geological laboratories; and (3) to determine that distributions in meteoritic samples appear more similar to prebiotic chemistry samples than they do to the terrestrial unaltered or diagenetic samples. Both diagenesis and putative interdisciplinary differences in analysis complicate interpretation of meteoritic amino acid distributions. We propose that the analysis of future samples from such diverse sources as meteoritic influx, sample return missions, and in situ exploration of Mars would be less ambiguous with adoption of standardized assay techniques, systematic inclusion of assay standards, and the use of a quantitative, probabilistic metric. We present here one such metric determined by sequential feature extraction and normalization (PCA), information-driven automated exploration of classification possibilities (HCA), and prediction of classification accuracy (ANNs).

Impurity profile of amino acids?

Amino acids are produced by various manufacturing processes, i.e. chemical and enzymatic synthesis, extraction from protein hydrolysates, and fermentation. Each process produces a different impurity profile. Since the European Pharmacopoeia wants to replace the non-selective and non-sensitive "ninhydrin-positive substance" TLC test with chromatographic or electrophoretic methods limiting the impurities to 0.1 per cent, the information about the production processes and the related impurity profile is urgently needed from the manufacturers.

Amino acid analysis by using comprehensive two-dimensional gas chromatography

The separation characteristics of alkylchloroformate-derivatised amino acids (AAs) by using comprehensive two-dimensional gas chromatography (GCxGC) is reported. The use of a low-polarity/polar column set did not provide as good a separation performance as that achieved with a polar/non-polar column set, where the latter appeared to provide less correlation over the separation space. The degree of component correlation in each column set was estimated by using the correlation coefficient (r(2); for (1)t(R) and (2)t(R) data) with the low-polarity/polar and polar/low-polarity sets returning correlation coefficients of 0.86, and 0.00 respectively, under the respective conditions employed for the experiments. The 1.5-m non-polar (2)D column (0.1-mm ID; 0.1-mum film thickness) gave peak halfwidths of the order of 50-80 ms. Linearity of detection was good, over a three order of magnitude concentration range, with typical lower detection limit of ca. 0.01 mg L(-1), compared with 0.5 mg L(-1) for normal GC operation with splitless injection. The method was demonstrated for analysis of AAs in a range of food and beverage products, including wine, beer and honey. The major AA in these samples was proline. The Heineken beer sample had a relatively more complex and more abundant AA content compared with the other beer sample. The wine and honey samples also gave a range of AA compounds. Repetition of the sample preparation/analysis procedure for the honey sample gave acceptable reproducibility for individual AAs.

Validation of accuracy-based amino acid reference materials in dried-blood spots by tandem mass spectrometry for newborn screening assays

BACKGROUND

Advances in technology and the earlier release of newborns from hospitals have pressed the demand for accurate calibration and improved interlaboratory performance for newborn screening tests. As a first step toward standardization of newborn screening aminoacidopathy tests, we have produced six-pool sets of multianalyte dried-blood-spot amino acid reference materials (AARMs) containing predetermined quantities of five amino acids. We describe here the production of the AARMs, validation of their amino acid contents, and characterization of their homogeneity and their stability in storage.

METHODS

To each of six portions of a pool of washed erythrocytes suspended in serum we added Phe (0-200 mg/L), Leu (0-200 mg/L), Met (0-125 mg/L), Tyr (0-125 mg/L), and Val (0-125 mg/L). Six-pool sets (1300) were prepared, dried, and packaged. We used isotope-dilution mass spectrometry to estimate the endogenous amino acid concentrations of the AARMs and validate their final amino acid concentrations. We used additional tandem mass spectrometry analyses to examine the homogeneity of amino acid distribution in each AARM, and HPLC analyses to evaluate the stability of the amino acid contents of the AARMs.

RESULTS

The absolute mean biases across the analytic range for five amino acids were 2.8-9.4%. One-way ANOVAs of the homogeneity results predicted no statistically significant differences in amino acid concentrations within the blood spots or within the pools (P >0.05). Regression slopes (0 +/- 0.01) for amino acid concentrations vs storage times and their P values (>0.05) showed no evidence of amino acid degradation at ambient temperatures, 4 degrees C, or -20 degrees C during the intervals tested.

CONCLUSION

The validation, homogeneity, and stability of these blood spots support their use as a candidate national reference material for calibration of assays that measure amino acids in dried-blood spots.

Artificial neural network prediction of amino acid levels in feed ingredients

Artificial Neural Networks (ANN), which are biologically inspired tools, serve as an alternative to regression analysis for complex data. Based on CP or proximate analysis (PA) of ingredients, two types of ANN and linear regression (LR) were evaluated for predicting amino acid levels in corn, wheat, soybean meal, meat and bone meal, and fish meal. The two ANN were a three layer Backpropagation network (BP3), and a General Regression Neural Network (GRNN). Methionine, TSAA, Lys, Thr, Tyr, Trp, and Arg were evaluated and R2 values calculated for each prediction method. Artificial neural network training was completed with NeuroShell 2 using Calibration to prevent overtraining. Ninety percent of the data were used as the input for the LR and the two ANN. The remaining 10% (randomly extracted data) were used to calibrate the performance of the ANN. As compared to LR, the R2 values were largest when PA input and GRNN were used. The BP3 did not consistently improve the R2 values for either CP or PA inputs as compared to LR. Each neural net can be incorporated into a computer or spreadsheet program.

Evaluation of National Research Council amino acid recommendations for large white turkeys

Two trials of identical experimental design were conducted to evaluate the NRC (1994) amino acid requirements for growing turkeys. Diets were formulated for 4-wk age intervals using intact ingredients and amino acid supplements to provide 85, 90, 95, 100, 105, 110, 115, and 120% of the suggested requirements. Formulation was done in a manner to minimize excess levels of as many essential amino acids as possible. Day-old male poults of a commercial Large White strain were grown to 20 wk on the test diets with body weight and feed conversion determined at intervals throughout the test; representative samples of birds were processed to determine carcass composition and parts yield. Results suggested that diets formulated to provide 105% of the suggested NRC requirements were needed to provide maximum body weight gain, feed conversion, and breast meat yield. Ambient temperatures in the present study frequently exceeded 27 C and may have contributed to the need for somewhat greater amino acid needs than the present NRC (1994) suggestions.

Effect of processing systems on protein quality of feather meals and hog hair meals

Experiments were conducted to evaluate the effects of five commercial processing systems and to a lesser extent, processing temperature within system, on protein quality of feather meals (FM). Two hog hair meals (HH) were also evaluated. True digestibilities of AA were determined with a 48-h excreta collection assay using cecectomized cockerels. Protein efficiency ratio (PER; grams of gain:grams of CP consumed) was determined with chicks by feeding Met-fortified 15% CP diets containing a FM or HH as the sole source of dietary protein. The six FM samples averaged 88.7% CP, 1.99% Lys, 4.83% Cys, and 0.71% Met on a DM basis. For HH, these values were 92.6, 2.78, 3.76, and 0.85%, respectively. True digestibilities of amino acids and PER of the FM varied among processing systems (e.g., lysine digestibility range was 58 to 72%, PER range was 0.71 to 1.13). Increasing the temperature during processing had no significant effect on protein quality of one FM and one HH. Digestibilities of AA in the FM water-soluble fraction collected after cooking were higher than those in the insoluble fraction. True amino acid digestibility coefficients for FM were higher than those for HH, whereas the PER of several FM were lower than those of HH. The latter response was probably due to the higher Lys content in the HH. The results of this study suggested that type of commercial processing system or conditions can affect the protein quality of FM.

Recent advances in methods of assessing dietary amino acid requirements for adult humans

The requirements for the indispensable amino acids have been determined by a number of different methods. Historically, descriptive or gross measures like growth and nitrogen balance have been used. However, technological advancements in recent years have resulted in the use of more precise and mechanistic metabolic approaches (i.e., plasma amino acid concentrations, amino acid oxidation, indicator amino acid oxidation) to examine requirement. Nevertheless, the current recommendations are still based on nitrogen balance studies. Requirement estimates based on other methodologies, such as plasma amino acid concentrations and direct amino acid oxidation, suggest that the requirement estimates derived from nitrogen balance experiments are too low. However, these higher estimates have also been criticized on conceptual and methodological grounds, resulting in considerable controversy in the area of indispensable amino acid requirements. A new technique, indicator amino acid oxidation, addresses many of the criticisms directed toward the alternative methods and the proposed higher requirement estimates. This paper reviews the current knowledge of amino acid requirements and makes recommendations in light of new information that has been provided from recent indicator amino acid oxidation research. It is concluded that the nitrogen balance-based estimates of amino acid requirement are too low.

The effect on energy and nitrogen metabolism by continuous, bolus, or sequential infusion of a defined total parenteral nutrition formulation in patients after major surgical procedures

BACKGROUND

The role of IV infusion kinetics to explain nutrition efficiency was investigated in patients after major surgical procedures.

METHODS

IV nutrition was provided as three different infusion kinetic regimens in a randomized fashion. All patients received nonprotein calories (100% of predicted preoperative REE, 60% D-glucose, 40% fat) and amino acid nitrogen (0.2 g N/d). Group A: Nutrition was provided by sequential infusion with combined fat and amino acids during daytime and glucose alone during nighttime ("sequential infusion"). Group B: Patients received 24-hour combined infusion with fat, amino acids, and glucose (all in one mixture) ("continuous infusion"). Group C: Nutrition was provided by bolus infusions during 1 hour followed by 2 hours without any infusion ("bolus infusion").

RESULTS

The daily energy balance was negative in all groups (-318 +/- 25 kcal/d, sequential infusion; -368 +/- 25 kcal/d continuous infusion; -292 +/- 20 kcal/d, bolus infusion). Significantly different excretion patterns of nitrogen in urine occurred among the groups despite an almost identical provision of nitrogen. Continuously infused patients retained nitrogen significantly better (-0.2 +/- 0.6 g/d) compared with sequentially (-3.4 +/- 1.0 g/d) and bolus-infused patients (-2.8 +/- 0.3 g/d) (p < .01), whereas their cumulative urinary glucose excretion was significantly larger. Continuously infused patients were in cumulative nitrogen balance during the entire postoperative period, whereas the other groups were in a significantly negative nitrogen balance. Urinary 3-methylhistidine excretion was similar in all groups.

CONCLUSIONS

The breakdown of muscle proteins was not sensitive to alterations in nutrient and substrate supply. Thus improved nitrogen retention reflected entirely improved synthesis. "All-in-one" IV nutrition with prolonged infusion periods is at present the most favorable regimen considering both the nutritional efficiency and its metabolic load on the organism after major surgery.

Do athletes need more dietary protein and amino acids?

The current recommended daily allowance (RDA) for protein is based primarily on data derived from subjects whose lifestyles were essentially sedentary. More recent well-designed studies that have employed either the classic nitrogen balance approach or the more technically difficult metabolic tracer technique indicate that overall protein needs (as well as needs for some specific individual amino acids) are probably increased for those who exercise regularly. Although the roles of the additionally required dietary protein and amino acids are likely to be quite different for those who engage in endurance exercise (protein required as an auxiliary fuel source) as opposed to strength exercise (amino acids required as building blocks for muscle development), it appears that both groups likely will benefit from diets containing more protein than the current RDA of 0.8 g.kg-1.day-1. Strength athletes probably need about 1.4-1.8 g.kg-1.day-1 and endurance athletes about 1.2-1.4 g.kg-1.day-1.

Sorghum amino acid-supplemented diets for the 50- to 100-kilogram pig

Three experiments were conducted to evaluate lysine (Lys), threonine (Thr), methionine (Met), tryptophan (Trp), and nonessential N (+N) supplementation of all sorghum grain (S) diets on growth and carcass characteristics of 50- to 100-kg pigs. In Exp. 1, four replicate pens of four pigs each were fed: 1) sorghum-soybean meal positive control (S-SBM); 2) S + Lys + Thr + Met + Trp to equal the amino acid concentrations in S-SBM (LTMT); 3) Diet 2 + N (LTMT+N); and 4) S negative control. Compared with pigs fed S-SBM, pigs fed LTMT or LTMT+N had reduced (P < .05) ADG, ADFI, serum urea N (SUN), pancreas weight, LMA, and percentage of muscling (PM) but higher dressing percentage (DP) and similar 10th rib fat thickness (TRF). Apparent N digestibility was lower (P < .05) in pigs fed LTMT than in pigs fed LTMT+N or S-SBM. In Exp. 2, two replicate pens of four pigs each were fed: 1) S-SBM; 2) S + Lys + Thr (LT); 3) S + Lys + Thr + Met (LTM); 4) S + Lys + Thr + Trp (LTT); 5) LTMT; 6 to 9) as 2 to 5 +N; and 10) S negative control. Compared with pigs fed S-SBM, pigs fed S, LT, LT+N, and LTM+N had lower (P < .05) ADG. Daily gain of pigs fed LTM, LTT, LTMT, LTT+N, or LTMT+N was not different (P > .10) from pigs fed S-SBM.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect on performance and carcass characteristics of nursery to finisher pigs fed reduced crude protein, amino acid-supplemented diets

An experiment was conducted to evaluate the effect of feeding reduced CP, amino acid (AA)-supplemented diets to pigs from weaning to slaughter weight on growth performance and carcass characteristics. Pigs were fed a 19%-16%-14% CP starter-grower-finisher high-CP sequence of diets, respectively, or a sequence of diets reduced in CP by 4 percentage units (3 percentage units in the finisher period) with or without lysine (LYS), tryptophan (TRP), and threonine (THR) supplementation. Pigs fed the low-CP diets without AA supplementation grew more slowly, were less efficient in feed conversion, and developed carcasses that contained a smaller longissimus muscle, greater, average backfat depths, and a lower percentage of muscle compared with pigs fed the high-CP sequence of diets (P < .01). The reduction in growth performance, feed efficiency, longissimus muscle area, and percentage of muscle in pigs fed the low-CP diets was alleviated by LYS, TRP, and THR supplementation (P > .10). Although pigs fed the low-CP diets supplemented with AA had reduced average and 10th rib backfat depths compared with pigs fed the unsupplemented, low-CP diets (P < .01), these fat depth measures remained greater (P < .05) than those of pigs fed the high-CP diets. Feeding reduced dietary CP, regardless of AA supplementation, resulted in reduced heart (P < .10) and liver weights (P < .01) compared with feeding the high-CP diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Micellar capillary electrophoresis separation and thermo-optical absorbance detection of products from manual peptide sequencing

Micellar capillary electrophoresis is optimized for separation of phenylthiohydantoin (PTH) amino acids produced in manual Edman degradation reaction for protein sequencing. There are also two major side-products produced by the Edman degradation reaction: diphenylthiourea and dimethylphenylthiourea. We report the complete separation of 19 PTH amino acids plus the two major side-reaction products in 10 min. Capillary electrophoresis is used to identify the five residues generated by manual Edman degradation sequencing of a pentapeptide.

Computer assisted neonatal parenteral nutrition solution protocols

Hospital pharmacies compound neonatal parenteral nutrition solutions for administration to premature infants until enteral feedings are tolerated. The majority of these solutions pose no problem for the hospital pharmacist to prepare. Occasionally, premature infants are prescribed low volume solutions that challenge the pharmacist to ensure the proper mixing and dilution of ingredients. Formulation and dilution protocols have been developed to guide the pharmacist in determining the safest procedure for compounding neonatal parenteral nutrition solutions. Staff members of Charlton Memorial Hospital pharmacy have developed a computer assisted calculation program that aids the pharmacist in following these protocols. Formulation changes suggested by the computer program should be verified by the pharmacist. Computerized documentation of formulation changes aid communication between the pharmacist and the physician. Infant safety is the primary goal of these formulation changes.

Internally standardized amino acid analysis for determining peptide/carrier protein coupling ratio

A method based on amino acid analysis has been developed for monitoring the covalent conjugation of synthetic peptide haptens to carrier proteins. The marker amino acid, alpha-aminobutyric acid, is included in the sequence during peptide synthesis. Following reaction, the carrier protein-conjugate is freed of excess peptide by two successive rounds of gel filtration chromatography. Amino acid analysis of a hydrolysate of the conjugate allows the calculation of the coupling ratio of the peptide to the carrier protein. Two typical procedures for conjugation, carbodiimide cross-linking and cysteine-thiol reaction with maleimidyl-proteins, have been evaluated.

Formation, nutritional value, and safety of D-amino acids

The extent of racemization of L-amino acid residues to D-isomers in food proteins increases with pH, time, and temperature. The nutritional utilization of different D-amino acids vary widely, both in animals and humans. In addition, some D-amino acids may be deleterious. For example, although D-phenylalanine is nutritionally available as a source of L-phenylalanine, high concentrations of D-tyrosine inhibit the growth of mice. The antimetabolic effect of D-tyrosine can be minimized by increasing the L-phenylalanine content of the diet. Similarly, L-cysteine has a sparing effect on L-methionine when fed to mice; however, D-cysteine does not. The wide variation in the utilization of D-amino acids is exemplified by the fact that D-lysine is not utilized as a source of L-lysine, whereas the utilization of D-methionine as a source of the L-isomer for growth is dose-dependent, reaching 76% of the value obtained with L-methionine. Both D-serine and the mixture of L-L and L-D isomers of lysinoalanine induce histological changes in the rat kidneys. D-tyrosine, D-serine, and lysinoalanine are produced in significant amounts under the influence of even short periods of alkaline treatment. Unresolved is whether the biological effects of D-amino acids vary, depending on whether they are consumed in the free state or as part of a food protein. Possible, metabolic interaction, antagonism, or synergism among D-amino acids in vivo also merits further study. The described results with mice complement related studies with other species and contribute to the understanding of nutritional and toxicological consequences of ingesting D-amino acids. Such an understanding will make it possible to devise food processing conditions to minimize or prevent the formation of undesirable D-amino acids in food proteins and to prepare better and safer foods.

Establishment of an external quality-assessment scheme for amino acid analyses: results from assays of samples distributed during two years

Ten different samples of lyophilized plasma and two of liquid urine were distributed during two years to 26 laboratories performing quantitative amino acid analyses in a scheme designed to provide external quality assessment. After each distribution, statistical summaries and performance scores based on delta standard deviations and percentage biases from the all-laboratory trimmed means were returned to participants, who also received annual performance summaries based on their accumulated results. Coefficients of variation calculated from returns across all the samples ranged from 13% for glycine to 65% for methionine. Automated ion-exchange amino acid analyzers with ninhydrin detection appeared to perform better than other methods, although there was no clearly superior method and no model of analyzer clearly outperformed the others. These exercises demonstrate that there is room for improvement in the performance of quantitative amino acid analyses and that individual expertise may be more important in maintaining good performance than the choice of method or analyzer.

Analysis of phenylthiohydantoin amino acid mixtures for sequencing by thermospray liquid chromatography/mass spectrometry

Phenylthiohydantoin (PTH) amino acids, the derivatives of amino acids liberated in the course of automated N-terminal sequence analysis of peptides and proteins, are most commonly identified by high-performance liquid chromatography. This communication describes an extension to the methodology for PTH amino acid identification which exploits thermospray liquid chromatography/mass spectrometry for use in the confirmation of PTH amino acid identifications previously made solely on the basis of retention times. Thermospray mass spectra of the 19 synthetic PTH amino acids corresponding to the residues commonly observed during N-terminal sequencing have been acquired. These spectra show strong signals for the protonated molecular ion, accompanied in several cases by ions produced by limited fragmentation of the amino acid side chain and/or the PTH ring system. A reverse-phase separation protocol has been adapted for use with thermospray. The method permits recognition of the protonated molecular ions of all the standard PTH amino acids at the 150-pmol level on the basis of signal-to-noise ratios of 10:1 or better with full scanning. The method has been tested on the N-terminal amino acid sequence analysis of 200 pmol of the standard protein beta-lactoglobulin A, and has been found useful in the study of selected side-products of the sequencing chemistry.

Quality control for amino acid visualization reagents

A method is described that quantitatively evaluates development conditions and reactivity of amino acid visualization reagents. Ninhydrin was the primary reagent used in this study. The method consists of spotting a serial dilution of amino acids in a numbered grid on paper. Examples of the variability of development as a result of atmospheric conditions are illustrated.

[Chemical evaluation of morro or jícaro (Crescentia alata) flours prepared by ensilaging and/or dehydration]

The chemical composition, nutritive value and potential use of the morro fruit (Crescentia alata) has received little attention. The purpose of the present study was: a) to determine appropriate conditions for processing and conservation of the morro fruit without hulls, since a significant part of the production is lost due to inadequate storage conditions, and b) to evaluate, by means of chemical analysis, the whole fruit and its products. For the preparation of dehydrated meals, the content of the fruit was subjected to sun drying and tray drying dehydration with two air temperatures, 60 degrees and 90 degrees C. The method used for the storage of the whole fruit was anaerobic fermentation achieved by ensilaging the fruit in small concrete experimental silos for 90, 145 and 180 days. At the end of each period, the silos were opened. The ensilaged material was of very good appearance and apparently free from unfavorable contaminations; it was dehydrated in tray dryers at an air temperature of 60 degrees C. Independent of processing, the chemical analysis showed the meals to contain on the average 17% crude fat, 11% crude fiber and 18% crude protein. From the amino acid content and using the 1973 FAO/WHO scoring pattern it was found that such flours were limiting in their sulfur amino acid, lysine and threonine content in the order.

Application of a simple method to the characterization and differentiation of protein foods

A screening method for the characterization and differentiation of proteinaceous samples and amino acid mixtures was applied to protein foods (4 protein-rich mixtures, one product sold as dietary supplement, and 3 raw materials of frequent use in the preparation of these products). Graphic profiles which describe the relative amounts of amino acid groups in the samples were obtained and subjected to statistical analysis. According to a previously established criterion of identity or difference, the correlation coefficients showed that at least 90% of the comparisons dealt with different samples. The method is proposed as a valuable tool for the quality control of protein-rich foods and their raw materials.

Computer analysis of amino acid chromatograms

A procedure is described for the automatic off-line analysis of amino acid chromatograms of protein hydrolysates, using a small computer. The data requirements are basic, and, unlike previous programs, the present system allows the separation and identification of bands, as well as the quantitative determination of composition. With minor modification, the program could be extended for use with most types of chromatographic data. The validity of the application of the program to experimental data is discussed.