Proteolytic activity and free amino acid concentrations in polymorphonuclear leucocytes

Extraction and analysis of free amino acids and 5'-nucleotides, the key contributors to the umami taste of seaweed

Assessing the umami taste of seaweed on a chemical level can inform the use and selection of seaweed in European cuisine. Accordingly, we developed a method for the simultaneous extraction, separate clean-up and analysis of 21 free amino acids and 10 free nucleotides by reversed phase and mixed-mode HPLC respectively. Of multiple mouth emulating solvents, extracting in Milli-Q at 35 °C was found most suitable. This method showed good linearity (R² > 0.9996), resolution (R_s ≥ 1.5) and picomole detection limits, and was successfully applied to determine the Equivalent Umami Concentration (EUC) and Taste Activity Values (TAV) of seven Dutch seaweed species. Phaeophyceae showed the highest EUC, followed by Chlorophyceae and Rhodophyceae (≈ 9.5, 3.7 and 1.1 g/100 g respectively). Glutamic acid always exceeded the TAV, while other umami compounds were species specific. Our method can accurately predict umami intensity and therefore contributes towards species selection for the European palette.

Quantitative determination of free intracellular alpha-keto acids in neutrophils

For the first time, a procedure is described for the quantitative analysis of free alpha-keto acid content in human neutrophils (PMNs) relative to single cell number by reversed-phase fluorescence high-performance liquid chromatography. The procedure is minimally invasive and is unsurpassed in the quality of PMN separation, ease of sample preparation as well as sample stability. This method can satisfy the rigorous demands for an ultra-sensitive, comprehensive and rapid intracellular alpha-keto acid analysis in particularly for the surveillance of severe diseases as well as cellular or organ dysfunction.

Free amino acids in plasma, red blood cells, polymorphonuclear leukocytes, and muscle in normal and uraemic children

BACKGROUND

The aims of this study were to investigate free amino acid (AA) concentrations in plasma, red blood cells (RBC), polymorphonuclear granulocytes (PMN), and muscle, sampled at the same time, in normal and uraemic children.

METHODS

Twelve apparently well-nourished chronically uraemic children (five females) aged a mean of 9.4+/-4.8 (range 1.7--17.7) years and 13 age-matched normal children were studied. Venous blood and muscle samples for AA analyses were taken simultaneously after an overnight fast.

RESULTS

The intracellular AA patterns in the three cellular compartments were qualitatively similar, but the absolute intracellular concentrations were higher in muscle than in PMN, which had higher values than in RBC. The AA patterns in plasma, RBC, PMN, and muscle in the uraemic children have many similarities; typical features being low branched-chain AA (BCAA), tyrosine, and serine concentrations and variably high concentrations of some non-essential AA. Among the individual AA, there were only few correlations between their concentrations in the three cell compartments.

CONCLUSIONS

The lack of correlation between the concentrations in RBC, PMN, and muscle for most of the AA indicates that there is no close association in the same subject between individual free AA concentrations in various types of cells, presumably because of differences in metabolism and function. Consequently, one should be cautious in assuming that AA concentrations, determined in RBC or PMN, reflect the concentrations in muscle cells. Therefore, these preliminary observations do not support the hypothesis that RBC and PMN AA analysis can be considered as a suitable alternative to muscle AA determination.

Quantitative determination of free intracellular amino acids in single human polymorphonuclear leucocytes. Recent developments in sample preparation and high-performance liquid chromatography

The described procedure allows quantitative, highly precise and reproducible analysis of free amino acid concentrations in single polymorphonuclear leucocytes (PMLs). This method is superior to previously described procedures with regard to sample size, PML separation, sample preparation and stability, as well as the chosen fluorescence high-performance liquid chromatography procedure, and can satisfy the high demands for ultra-sensitive and comprehensive amino acid analysis, especially for the continuous surveillance of severe diseases and organ dysfunction.