1997 UK Total Diet Study--dietary exposures to aluminium, arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, tin and zinc.

Concentrations of aluminium, arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, tin and zinc were determined in samples from the 1997 UK Total Diet Study and used to estimate dietary exposures of the general UK population. Population average dietary exposures to aluminium (3.4 mg/day), arsenic (0.065 mg/day), cadmium (0.012 mg/day), chromium (0.10 mg/day), copper (1.2 mg/day), mercury (0.003 mg/day), nickel (0.13 mg/day), tin (1.8 mg/day) and zinc (8.4 mg/day) are similar to those from previous UK Total Diet Studies and are below the appropriate PTWIs, PMTDIs and TDIs. Dietary exposure of the UK population (0.026 mg/day) to lead is falling as a result of measures taken to reduce lead contamination of the environment and food and is well below the PTWI. There has been little change in UK estimates of selenium exposure since the 1994 Total Diet Study but current-estimates (0.039 mg/day) are lower than those derived from earlier Total Diet Studies.

Dietary exposure estimates of 30 elements from the UK Total Diet Study.

Dietary exposures of consumers to 30 elements (aluminium, antimony, arsenic, barium, bismuth, boron, cadmium, calcium, chromium, cobalt, copper, germanium, gold, iridium, iron, lead, lithium, manganese, mercury, molybdenum, nickel, palladium, platinum, rhodium, ruthenium, selenium, strontium, thallium, tin and zinc) estimated from the UK 1994 Total Diet Study are reported, and compared with those from previous UK Total Diet Studies and those from other countries. Dietary exposure estimates were generally low and, where comparisons are possible, similar to those from other countries and below the relevant Provisional Tolerable Weekly Intakes and Provisional Maximum Tolerable Daily Intakes. For most of those elements included in previous UK Total Diet Studies, dietary exposures have declined.

Monitoring for nitrate in UK-grown lettuce and spinach.

To comply with European Commission requirements, the UK is carrying out a monitoring programme on nitrate concentrations in lettuce and spinach. This paper reports the results obtained between June 1996 and April 1998. A total of 182 samples of protected lettuce, 131 samples of outdoor-grown lettuce and 34 samples of fresh spinach were taken from the main growing areas of the UK. Nitrate concentrations in protected lettuce were influenced by the season with summer-grown crops (mean of 2382 mg/kg) having lower levels than those grown in the winter (mean of 3124 mg/kg). Weather conditions also affected concentrations in protected lettuces with long hours of sunshine and low rainfall associated with low nitrate levels. Nitrate concentrations in outdoor-grown lettuces were lower (mean of 1085 mg/kg) than those in protected lettuces but there were insufficient data to determine if they were affected by the weather conditions or season. Similarly there were insufficient data to determine if weather conditions or season influenced nitrate concentrations in spinach (mean of 1900 mg/kg) but regional differences were observed.

Dietary exposures to nitrate in the UK.

Dietary exposures to nitrate have been estimated for two different groups of UK consumers. The daily dietary exposure of the general population was estimated from the UK 1997 Total Diet study to be 52 mg/day. Vegetables contributed approximately 70% to this total dietary exposure. Dietary exposure estimates for adult consumers of vegetables commonly eaten in the UK were 93 mg/day and 140 mg/day for mean and 97.5th percentile consumers, respectively. Dietary exposures to nitrate of UK consumers are similar to those in other European countries and are less than the Acceptable Daily Intake (ADI) for nitrate set by the European Commission's Scientific Committee for Food.

Serum factors, growth factors and UDP-sugar metabolism in bovine articular cartilage chondrocytes.

1. The effect of different batches of fetal bovine serum and of growth factors on [35S]sulphate incorporation into glycosaminoglycans and on UDP-sugar pools in explant cultures of bovine articular cartilage was investigated. 2. [35S]Sulphate incorporation was variably stimulated between 1.2- and 3.5-fold by four different batches of serum. The UDP-glucuronate pool size expanded 4.3-6.5-fold in the presence of serum, even in those cultures in which little stimulation of [35S]sulphate incorporation occurred. The UDP-N-acetylhexosamine and UDP-hexose pools expanded by about 1.5- and 2.0-fold respectively in the presence of serum. UDP-xylose was not detected. 3. Equilibrium-labelling and pulse-chase experiments with D-[1-3H]glucose indicated that the rate of flux through the UDP-sugar pools was unaffected by serum. UDP-hexose, UDP-N-acetylhexosamine and UDP-glucuronate have approximate half-lives (t1/2) of 7, 12 and 3-4 min respectively. At equilibrium, the 3H specific activities of UDP-hexose and UDP-N-acetylhexosamine were very similar but that for the UDP-glucuronate pool was much higher, especially in serum-supplemented cultures. The results suggest that UDP-glucuronate synthesis occurs via a pathway which is independent of the main UDP-hexose pathway. 4. Supplementing cultures with heat-treated serum had no effect on the serum-induced expansion of UDP-sugar pools but stimulation of [35S]sulphate incorporation into glycosaminoglycans was 50% lower than for native serum. Acid-treated serum promoted a 2-fold expansion of the UDP-glucuronate and UDP-N-acetylhexosamine pool over that obtained with native serum but was 20% less effective in stimulating [35S]sulphate incorporation than the latter. Prior dialysis of serum had no effect on its modulatory action on either [35S]sulphate incorporation or on the size of UDP-sugar pools. 5. Insulin-like growth factor 1 (IGF-1), transforming growth factor beta-1 (TGF beta-1), platelet-derived growth factor (PDGF) (BB homodimer) and epidermal growth factor (EGF) all stimulated [35S]sulphate incorporation into glycosaminoglycans as expected. The UDP-glucuronate pool expanded by 1.5- and 2.0-fold in the presence of IGF-1 and TGF beta-1 respectively, and by about 1.8-fold in the presence of PDGF or EGF. None of the factors investigated, or combinations of IGF-1 and TGF beta-1 or IGF-1 and EGF, stimulated expansion of the UDP-glucuronate pool to the same extent as native serum.(ABSTRACT TRUNCATED AT 400 WORDS)

Responses of articular cartilage explant cultures to different oxygen tensions.

Bovine articular cartilage explants were cultured under atmospheres of 6, 10, 24, 66 and 91% oxygen. [35S]Glycosaminoglycan, chondroitin sulphate and keratan sulphate synthesis were measured together with the pool size of UDP-N-acetylhexosamines, UDP-hexoses and UDP-glucuronate. UDP-xylose was not detected. [35S]Glycosaminoglycan synthesis was maintained at the same level as in fresh tissue when cultured over 7 days with 20% foetal calf serum present and under a 6% oxygen tension. Under normal atmosphere (24%) synthesis was stimulated and remained elevated throughout the incubation period. Under higher oxygen tensions, initial stimulation of glycosaminoglycan synthesis was followed by progressive inhibition. The [35S]chondroitin sulphate/keratan sulphate ratio was constant (approximately 16:1) between 6 and 24% oxygen tension, but increased to 50:1 at 91% oxygen. The UDP-N-acetylhexosamine pool was larger under anaerobic (6, 10%) and excessively aerobic (66, 91%) oxygen tensions than under a normal atmosphere (24%). The UDP-hexose pool was expanded under anaerobic conditions. The UDP-glucuronate pool showed little variation between 6 and 24% oxygen tensions, but contracted under very aerobic conditions. We found no evidence indicating that keratan sulphate synthesis was favoured under anaerobic conditions to compensate for decreasing chondroitin sulphate synthesis.