Oral zinc augmentation with vitamins A and D increases plasma zinc concentration: implications for burden of disease.

A study evaluating zinc supplementation in patients with Alzheimer's disease yielded variable zinc plasma levels in spite of positive cognitive and physiological results. In an attempt to raise and sustain plasma zinc levels, a single patient was given 15 mg zinc/day with various combinations of vitamins. A sustained raise in plasma zinc concentration (and therefore its potential bioavailability) was obtained only when the zinc was augmented with both vitamins A and D (in RDA concentrations). In order to verify these results, a follow-up study was conducted in 70 volunteers. Seven groups of 10 healthy subjects received various combinations of zinc and the two vitamins A and D, namely: zinc, vitamin A, vitamin D, zinc plus vitamin A, zinc plus vitamin D, vitamins A and D, and zinc plus vitamins A and D. Plasma zinc levels were determined at baseline, 3 weeks and 6 weeks. Plasma zinc levels increased significantly (p < 0.02) from 11.82 (+/-2.60) to 13.32 (+/-3.04) mum/L only in the group receiving the combination of zinc and vitamins A and D. This novel method of increasing plasma zinc levels by the augmentation of vitamins A and D may have implications for the reduction of burden of disease.

A rapid method of monitoring the acute phase response in a rat model.

The acute phase response (APR) is accompanied by major changes in micronutrient status. It is important to be able to quantitate the degree of APR, which can then be related to the accompanying alterations in micronutrient levels. A rapid and convenient means of achieving this, viz. the use of an animal model in which APR can be induced, would facilitate such an investigation. The aim of the present study was to establish, by means of a rat model, a rapid procedure to identify APR which is less time-consuming and less expensive than the more traditional enzyme-linked immunosorbent assay and radio-immunoassay. Blood was drawn immediately prior to, and at 24, 48, 72 and 96-hour intervals post-inducement of the acute phase. The serum was deproteinised and treated with a dye, Auramine O, which specifically binds the acute phase protein alpha 1-acid glycoprotein (AAG), the latter remaining in solution after deproteinisation. The product formed is a fluorescent addition compound. With fluorescence spectrophotometry, levels of AAG were determined and the extent of APR monitored. A progressive and reproducible increase in AAG was observed, the highest fluorescence intensity recorded after 48 hours; this indicated a mean value (N = 5) of 9.4 mg/ml from zero at baseline. With a spiking approach, a mean AAG recovery of 96% was obtained. The validated methodology, less expensive and less time-consuming than existing procedures, which rapidly detects AAG in rat serum, provides a simple technique for monitoring the APR process in these animals.

Determination of plasma amino acids by gas chromatography.

A complete methodology, incorporating a novel clean-up technique, for quantitative determination of amino acids in plasma by gas chromatography is described. Glucose, a component causing major analytical interference, is removed by an enzymic reaction included in the pre-chromatographic clean-up. The procedure for derivatisation of amino acid standards is shown to be reproducible down to a level of 2.5 micrograms for each amino acid, relative standard deviations for all amino acids except arginine and histidine being 3% or lower. For the entire procedure applied to plasma, relative standard deviations for most amino acids are below 5% with recoveries ranging from 90 to 120%. Normal values, obtained using eighteen plasma samples, are in reasonable agreement with published data. Plasma amino acid values were determined simultaneously by gas chromatographic and ion-exchange chromatographic techniques. Statistical evaluation shows there to be no significant difference between corresponding values for eleven amino acids. Values for tyrosine, histidine and particularly phenylalanine show significant differences (p less than 0.001).

Gas chromatographic analysis of amino acids in physiological fluids: a critique.

The available methodology for sample purification prior to gas chromatographic analysis of amino acids in physiological fluids and tissue extracts is analysed. It would appear that over the past ten years the method of choice is that of an ion-exchange purification step, and little, if any, progress has been achieved in sample purification procedures. The inherent disadvantages of such a methodology are not only perpetuated but also cast some considerable doubt on the accuracy of the quantitative analysis of amino acids.

Gas-liquid chromatography of amino acids. Determination of cystine and cysteine as N-acetyl, n-propyl S-carboxymethylcysteinate.

A procedure is described for the derivatisation of S-carboxymethylcysteine yielding the corresponding N-acetyl, n-propyl S-carboxymethylcysteinate which is separated by gas chromatography form similar derivatives of other protein amino acids. Its quantitative determination provides a useful extension to a method for analysis of amino acids by gas chromatography and offers potential as a means of obviating errors in cystine (and/or cysteine) analysis arising from acid hydrolysis of proteins.

Tyramine content of South African cheeses.

The tyramine content of certain South African cheeses has been determined by gas chromatographic analysis. Aged (mature) cheese such as cheddar and Roquefort contain relatively large concentrations of tyramine as compared with other cheese, especially cottage cheese. Foods containing pressor amines must be avoided by certain patients.