Platelet dysfunction contributes to the haemostatic defect in haemorrhagic fever with renal syndrome.

To characterize further the nature of haemostatic impairment in haemorrhagic fever with renal syndrome, we assessed platelet function in 9 patients in whom the diagnosis was serologically confirmed. Defective platelet aggregation was demonstrated in every patient. An abnormality of the granule release reaction was demonstrated in all of 7 patients tested. Gel-filtered platelets from a normal subject showed normal aggregation in plasma from a patient with impaired aggregation, which is evidence for an intrinsic platelet defect, and against the presence of a circulating inhibitor in this patient.

Changes in populations of immune effector cells during the course of haemorrhagic fever with renal syndrome.

To characterize the immune response in haemorrhagic fever with renal syndrome, serial changes in immune effector cells were measured in 14 patients. Significant findings included initial elevations of all major leucocyte populations, increases in suppressor T cells and B cells, decreases in helper/suppressor cell ratios, and a dramatic increase in activated T cells. These changes were most marked in severely ill patients. Changes reverted to normal over approximately one week.

Effects of grinding and storage for one month on retention of vitamin A in premixes and mineral supplements.

Tested standardized procedures for handling premixes and mineral supplements from time of sampling to time of analysis for vitamin A have not been developed, which could account for some unexplained inconsistent and low analytical results. Grinding premix samples and storing them in a freezer for one month had little effect on amount of vitamin A found, but there was a significant loss (about 10%) after storage for one month at room temperature. Results on replicated determinations of vitamin A in unground and ground mineral supplements and on effect of storage were somewhat more variable than for premixes, but only the loss (about 12%) during storage for one month at room temperature was significant.

Modification of the method for vitamin A in foods and feeds for use with margarine and butter: collaborative study.

An adaptation of the method for vitamin A in feeds and foods to margarine and butter was studied in 1977 and 1978. The principal change was the use of 2 extractions with an ether-hexane mixture instead of one with hexane. Results of the 1977 test were not good enough to recommend adoption. The 1978 analytical samples consisted of 4 margarines, including a known, and a butter. Data were reported by 11 analysts. Averages for vitamin A (microgram/g) and coefficients of variation (%) were, respectively: A (known)--7.2, 5.7; 1--8.2, 11.1; 2--11.4, 3.9; 3--7.6, 10.7; butter--8.5, 13.3; and for carotene: A--5.6, 6.4; 1--6.0, 5.5; 2--0; 3--5.8, 3.8; butter--3.1, 11.8. Carotene results were grouped reasonably closely and tended to be distributed randomly, but vitamin A results had a less random trend. Trifluoroacetic acid was studied as an alternative colorimetric reagent for determining vitamin A, with overall satisfactory results. The modification for determining vitamin A and carotene in butter and margarine, and the use of trifluoroacetic acid as an alternative colorimetric reagent have been adopted as official first action.

Determination of vitamin E in foods--a review.

The vitamin E group includes tocopherols and tocotrienols and their isomers, esters, and derivatives. They differ not only in biopotencies as antisterility agents but also in activities in other physiological and chemical relationships. Unlike vitamins A and D, foods (vegetable oils) are among the richest sources of vitamin E, and assay methods for vitamin E include food applications more often than for the former vitamins. Physicochemical methods are replacing bioassays for vitamin E and tocopherol wherever possible because of greater specificity and less variability, time, and, sometimes, expense. Unless careful purifications and isolations are carried out and some of the relative vitamin E activities of components are calculated, bioassays are still required for total vitamin E activity. The vitamin E group is separated by column, paper, thin-layer, gas-liquid, and high-pressure liquid chromatography (HPLC). Gas-liquid chromatography has been more successfully used for vitamin E than for other fat-soluble vitamins. Recently developed HPLC methods for vitamin E are sensitive and apparently require less cleanup of extracts and less time than former methods; HPLC may prove to be the most useful technique for vitamin E in foods, especially if other fat-soluble vitamins can be determined simultaneously on the same sample extract.

Determination of vitamin K in foods: a review.

Vitamin K receives less dietary attention and fewer assays in foods than other fat-soluble vitamins. It is widely distributed in foods, usually at low concentrations. The human requirement is small. Intestinal bacteria synthesize vitamin K, which presumably helps provide the metabolic requirements for vitamin K. An RDA for vitamin K has not been published, but infants fed milk-substitute formulas risk vitamin K deficiency and it is recommended that those formulas contain supplemental vitamin K. Vitamin K in foods includes phylloquinone (K1) found in plants and several menaquinones (K2) found in animals and synthesized by microorganisms. Many vitamin K methods were developed primarily to identify forms present and determine their relative bioactivities. Until recently bioassays with chicks were the only practical methods to determine vitamin K content of foods. Various physicochemical methods have been developed to determine vitamins K in pure solutions, concentrates, and pharmaceuticals. Because of low concentrations of vitamin K in foods and the extensive purifications of extracts required, there has been only limited use of physicochemical methods, such as column chromatography, thin-layer chromatography, and high-performance liquid chromatography, with foods; the latter method perhaps offers the greatest possibilities for further development.

Determination of vitamin D in foods: a review.

Determining vitamin D content in foods is difficult because in natural foods of highest vitamin D activity, and even in vitamin D-fortified foods, only small quantities are present, and many other compounds are extracted along with vitamin D that cause difficulties in purifying the extract or in the spectrophotometry or colorimetry that follows. Several physicochemical methods--such as spectrophotometric, colorimetric, thin-layer chromatographic, adsorption, partition, gas-liquid, and high-performance column chromatographic--have been tried for assay foods for vitamin D, but none of them have been accepted for official or routine use; they are time consuming and expensive, or lack the required sensitivity, precision, or accuracy. Curative biological assays, based on degree of healing of a leg bone of rats previously made rachitic, is the generally accepted method to determine vitamin D content of foods. However, that method also requires too much time and is expensive. The recently developed high-performance liquid chromatographic method may offer the most for establishing a satisfactory physicochemical method for determining vitamin D in foods. Many of the difficulties and problems in assaying foods for vitamin D are discussed.

Determination of vitamin A in foods--a review.

Formerly, few foods were routinely analyzed for vitamin A, but recent emphasis on nutrient requirements, nutrient labeling, and use of dietary convenience foods has created need for determining vitamin A in a variety of foods. There are many vitamin A methods--some suitable for certain products only. For regulatory purposes, the FDA specifies the AOAC method where it is applicable. However, some food analysts and organizations continue with their own vitamin A methods. If possible, a single, widely applicable general method should be used for vitamin A in foods. Vitamin A may be determined by spectrophotometric, colorimetric, and fluorometric procedures. Sometimes chromatography is required as an important part of the method. Colorimetric procedures with SbCl3 are now most widely used to measure vitamin A (retinol) in foods. If vitamin A content is high enough and extracts sufficiently free of interfering substances, spectrophotometric or flurometric methods are satisfactory. Methods in various stages of development for determining vitamin A in foods are based on flurospectrophotometry, gas-liquid chromatography, high-performance liquid chromatography, and automation. To estimate total vitamin A nutritional value of certain foods may also require determination of vitamin A isomerization and contents of carotenes, cryptoxanthin, reinaldehyde, and apo-carotenal.

Colorimetric reagents for determining vitamin A in feeds and foods.

Selected blue-color developing reagents for determining vitamin A, effects of some carotenoids, tocopherol, and sterols commonly found in vitamin A extracts of feeds and foods, and effects of moisture and light on the colors developed under normal laboratory conditions were studied. Similar blue colors were obtained using SbCl3, CF3COOH, and CCl3COOH in solutions of CHCl3, CH2Cl2 and C2H4Cl2. In general, the reagents in CH2Cl2 solutions produced the most stable blue colors. The CCl3COOH-in-CH2Cl2 reagent developed slightly higher initial color, but CCl3COOH, especially in CHCl3 solution, was the least stable reagent. Small amounts of moisture affected only SbCl3 reagents, by forming cloudy solutions and precipitates. Carotene and monohydroxy and dihydroxy carotenoids reacted with all reagents tested to produce bluish colors, which, however, reached maximum development much later than the vitamin A blue colors. The presence of sterols slightly decreased color production of vitamin A solutions and frequently slightly increased rate of fading, especially for SbCl3 reagents. With proper precautions any of the reagents studied may be used to determine vitamin A. The preferred reagent for general use probably is CF3COOH-in-CH2Cl2, but it is not the most economical.