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1.
Heat and alkali treatments of foods, widely used in food processing, result in the formation of dehydro and cross-linked amino acids such as dehydroalanine, methyldehydroalanine, beta-aminoalanine, lysinoalanine (LAL), ornithinoalanine, histidinoalanine (HAL), phenylethylaminoalanine, lanthionine (LAN), and methyl-lanthionine present in proteins and are frequently accompanied by concurrent racemization of L-amino acid isomers to D-analogues. The mechanism of LAL formation is a two-step process: first, hydroxide ion-catalyzed elimination of H(2)S from cystine and H(2)O, phosphate, and glycosidic moieties from serine residues to yield a dehydroalanine intermediate; second, reaction of the double bond of dehydroalanine with the epsilon-NH(2) group of lysine to form LAL. Analogous elimination-addition reactions are postulated to produce the other unusual amino acids. Processing conditions that favor these transformations include high pH, temperature, and exposure time. Factors that minimize LAL formation include the presence of SH-containing amino acids, sodium sulfite, ammonia, biogenic amines, ascorbic acid, citric acid, malic acid, and glucose; dephosphorylation of O-phosphoryl esters; and acylation of epsilon-NH(2) groups of lysine. The presence of LAL residues along a protein chain decreases digestibility and nutritional quality in rodents and primates but enhances nutritional quality in ruminants. LAL has a strong affinity for copper and other metal ions and is reported to induce enlargement of nuclei of rats and mice but not of primate kidney cells. LAL, LAN, and HAL also occur naturally in certain peptide and protein antibiotics (cinnamycin, duramycin, epidermin, nisin, and subtilin) and in body organs and tissues (aorta, bone, collagen, dentin, and eye cataracts), where their formation may be a function of the aging process. These findings are not only of theoretical interest but also have practical implications for nutrition, food safety, and health. Further research needs are suggested for each of these categories. These overlapping aspects are discussed in terms of general concepts for a better understanding of the impact of LAL and related compounds in the diet. Such an understanding can lead to improvement in food quality and safety, nutrition, microbiology, and human health. 相似文献
2.
Bioaccumulation of trace metals in plant tissues can present a health risk to wildlife, and potentially to humans. The Passamaquoddy tribe in Maine was concerned about health risks of cadmium (Cd) because of a health advisory for moose liver and kidney consumption due to high Cd levels. This study found relatively low to moderate concentrations of Cd, nickel (Ni), lead (Pb), and zinc (Zn) concentrations in four common terrestrial moose browse species, associated forest soils, and two species of aquatic vegetation on Passamaquoddy tribal land in eastern Maine. Terrestrial plant tissue concentrations ranged from 0.1 to 1.97, 0.65 to 7.08, 0.29 to 2.0, and 42 to 431 mg kg ?1 for Cd, Ni, Pb and Zn, respectively. Deciduous species, particularly aspen and birch, may be a more significant source of Cd and Zn to wildlife compared to coniferous or aquatic species. Aquatic plant tissue concentrations ranged from 0.11 to 0.14, 0.46 to 1.01, 0.8 to 0.9, and 22 to 41 mg kg ?1 for Cd, Ni, Pb and Zn, respectively. Total O horizon concentration means for coniferous and deciduous were 0.50 and 1.00, 4.27 and 4.11, 55 and 21, and 55 and 167 mg kg ?1 for Cd, Ni, Pb and Zn, respectively. The study provides baseline vegetation and soil trace metal concentrations for a remote region in Maine impacted by non-point sources. 相似文献
3.
Abstract Applications of zinc (Zn) and copper (Cu) at excessive rates may result in phytotoxicity. Experiments were conducted with mixtures of soils that were similar except for their Zn and Cu levels. The critical toxicity levels (CTL) in the soils and plants for these elements were determined. Peanut ( Arachis hypogaea L.), soybean [ Glycine max (L.) Merr.], corn ( Zea mays L.), and rice ( Oryza sativa L.) were the crops grown. One soil mixture had Mehlich 3‐extractable Zn concentrations up to 300 mg dm ‐3 with no corresponding increase in soil Cu; two soil mixtures had soil Zn concentrations up to 400 and 800 mg dm ‐3 with a corresponding increase in soil Cu up to 20 and 25 mg dm ‐3, respectively; and four soil mixtures had no increase in soil Zn, but had Mehlich 1‐extractable Cu concentrations from 6 to 286 mg kg ‐1. Under a given set of greenhouse conditions, the estimated Mehlich 3‐extractable Zn CTL was 36 mg dm ‐3 for peanut, 70 mg dm ‐3 for soybean, between 160 and 320 mg dm ‐3 for rice, and >300 mg dm ‐3 for corn. No soil Cu CTL was apparent for peanut or soybean, but for corn it was 17 mg dm ‐3 and for rice 13 mg dm ‐3. With different greenhouse procedures and the Mehlich 1 extractant, the soil CTL for rice was only 4.4 mg kg ‐1. Therefore, peanut and soybean were more sensitive to Zn toxicity, whereas corn and rice were more sensitive to Cu toxicity. Plant Zn CTL for peanut was 230 mg kg ‐1, while that for soybean was 140 mg kg ‐1. Copper appeared to be toxic to corn and rice at plant concentrations exceeding 20 mg kg ‐1. 相似文献
4.
Nitrofurans were broadly used as an extremely effective veterinary antibiotic especially in pig and poultry production farms. Because of fears of the carcinogenic effects on humans, the nitrofurans were banned from use in livestock production in many countries, including the European Union. The present study examines the accumulation, distribution, and depletion of furaltadone and nifursol and of their tissue-bound metabolites [3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ) and 3,5-dinitro-salicylic acid hydrazine (DNSAH), respectively, in poultry edible tissues (muscle, liver, and gizzards) following administration to chickens of therapeutic and subtherapeutic concentrations of both compounds. Nitrofurans determination was performed by high-performance liquid chromatography-diode array detection and liquid chromatography-tandem mass spectrometry, respectively, for feeds and for poultry tissues. Furaltadone and nifursol, in very low concentrations, were found in samples of muscle, liver, and chicken's gizzard collected from slaughtered animals after 5 weeks of treatment and no withdrawal time period. When a withdrawal time period of 3 weeks was respected, no detectable nitrofuran parent compounds was observed in all of the studied matrices. For AMOZ, concentrations of 270 μg/kg in meat, 80 μg/kg in liver, and 331 μg/kg in gizzard were determined after administration of a medicated feed with furaltadone (132 mg/kg), 3 weeks after withdrawal of treatment. For DNSAH, the concentration values obtained are much lower than those observed for AMOZ. For meat, liver, and gizzard, DNSAH concentrations of 2.5, 6.4, and 10.3 μg/kg, respectively, were determined, after administration of a medicated feed with nifursol (98 mg/kg), 3 weeks after withdrawal of treatment. The gizzard could be considered a selected matrix for nitrofuran residues evaluation in poultry, due to its capacity of retaining either nitrofuran parent compounds or metabolites in higher concentrations, regardless of the administered dose or of the respected withdrawal time period. 相似文献
5.
Amazonia, the world's largest tropical rain forest, is often assumed to be a virtually untouched wilderness. The region is often referred to as a demographic void; there is on average only about one person per sq. km. Yet in response to international market forces, the hand of man has penetrated deep into the imposing forests. Since colonial times, wildlife, particularly along rivers, has been exploited on a large-scale basis for commercial purposes. This paper focuses on the effects of the trade on some aquatic animals. 相似文献
6.
Among plant-derived odorants, damascenone is one of the most ubiquitous, sometimes occurring as an apparent natural product but more commonly occurring in processed foodstuffs and beverages. It has been widely reported as a component of alcoholic beverages, particularly of wines made from the grape Vitis vinifera . Although damascenone has one of the lowest ortho- and retronasal detection thresholds of any odorant, its contribution to the sensory properties of most products remains poorly understood. Damascenone can be formed by acid-catalyzed hydrolyses of plant-derived apocarotenoids, in both aglycon and glycoconjugated forms. These reactions can account for the formation of damascenone in some, but not all, products. In wine, damascenone can also be subject to degradation processes, particularly by reaction with sulfur dioxide. 相似文献
9.
To answer the need for simple, economical, rapid methods for mycotoxins, a procedure for screening and quantitation of ochratoxin A was developed. A methanol-aqueous KCl extraction is used, followed by cleanup with clarifying agents and partition into chloroform. Part of the chloroform extract is used for screening and the other part for quantitation by thin layer chromatography (TLC). The screening procedure takes 40 min, using a silica gel/aluminum oxide minicolumn developed for this purpose. The limits of detection are 80 and 10 micrograms/kg, respectively, for minicolumn screening and TLC quantitation. Ammonium sulfate is efficient in cleaning samples of corn and cassava; cupric sulfate is better with peanuts, beans, and rice. Tests were conducted on triplicate spiked samples of yellow corn meal, raw peanuts, dried black beans, polished rice, and cassava flour at different levels (400, 200, 80, 40, and 10 micrograms/kg). Recoveries ranged from 86 to 160% and the coefficients of variation ranged from 0 to 26%. 相似文献
10.
Nine stream sites in the Blackfoot River watershed in southeastern Idaho were sampled in September 2000 for water, surficial sediment, aquatic plants, aquatic invertebrates, and fish. Selenium was measured in these aquatic ecosystem components, and a hazard assessment was performed on the data. Water quality characteristics such as pH, hardness, and specific conductance were relatively uniform among the nine sites examined. Selenium was elevated in water, sediment, aquatic plants, aquatic invertebrates, and fish from several sites suggesting deposition in sediments and food web cycling through plants and invertebrates. Selenium was elevated to concentrations of concern in water at eight sites (>5 g/L), sediment at three sites (>2 g/g), aquatic plants at four sites (>4 g/g), aquatic invertebrates at five sites (>3 g/g), and fish at seven sites (>4 g/g in whole body). The hazard assessment of selenium in the aquatic environment suggested low hazard at Sheep Creek, moderate hazard at Trail Creek, upper Slug Creek, lower Slug Creek, and lower Blackfoot River, and high hazard at Angus Creek, upper East Mill Creek, lower East Mill Creek, and Dry Valley Creek. The results of this study are consistent with results of a previous investigation and indicate that selenium concentrations from the phosphate mining area of southeastern Idaho were sufficiently elevated in several ecosystem components to cause adverse effects to aquatic resources in the Blackfoot River watershed. 相似文献
11.
The concentrations of Hg, Cu, Pb, Cd, and Zn accumulated by regional macrophytes were investigated in three tropical wetlands in Colombia. The studied wetlands presented different degrees of metal contamination. Cu and Zn presented the highest concentrations in sediment. Metal accumulation by plants differed among species, sites, and tissues. Metals accumulated in macrophytes were mostly accumulated in root tissues, suggesting an exclusion strategy for metal tolerance. An exception was Hg, which was accumulated mainly in leaves. The ranges of mean metal concentrations were 0.035?C0.953 mg g ?1 Hg, 6.5?C250.3 mg g ?1 Cu, 0.059?C0.245 mg g ?1 Pb, 0.004?C0.066 mg g ?1 Cd, and 31.8?363.1 mg g ?1 Zn in roots and 0.033?C0.888 mg g ?1 Hg, 2.2?C70.7 mg g ?1 Cu, 0.005?C0.086 mg g ?1 Pb, 0.001?C0.03 mg g ?1 Cd, and 12.6?C140.4 mg g ?1 Zn in leaves. The scarce correlations registered between metal concentration in sediment and plant tissues indicate that metal concentrations in plants depend on several factors rather than on sediment concentration only. However, when Cu and Zn sediment concentrations increased, these metal concentrations in tissues also increased in Eichhornia crassipes, Ludwigia helminthorriza, and Polygonum punctatum. These species could be proposed as Cu and Zn phytoremediators. Even though macrophytes are important metal accumulators in wetlands, sediment is the main metal compartment due to the fact that its total mass is greater than the corresponding plant biomass in a given area. 相似文献
12.
The results of residue determinations of the growth promotors carbadox, tylosin, and virginiamycin in kidney, liver, and muscle from pigs in feeding experiments are described as well as the analytical methods used. Residues of the carbadox metabolite quinoxaline-2-carboxylic acid were found in liver from pigs fed 20 mg/kg in the diet with a withdrawal time of 30 days. No residues were detected in muscle with zero withdrawal time. The limit of determination was 0.01 mg/kg for both tissues. No residues of virginiamycin and tylosin were found in pigs fed 50 and 40 mg/kg, respectively, in the diet, even with zero withdrawal time. Residues of tylosin of 0.06 mg/kg and below were detected in liver and kidney from pigs fed 200 or 400 mg/kg and slaughtered within 3 h after the last feeding. 相似文献
13.
Quantitative data with regard to dietary (3R,3'R,6'R)-lutein, (3R,3'R)-zeaxanthin, and their (E/Z)-geometrical isomers are scarce, and in most cases, only the combined concentrations of these two carotenoids in foods are reported. Lutein and zeaxanthin accumulate in the human macula and have been implicated in the prevention of age-related macular degeneration (AMD). The qualitative and quantitative distributions of lutein, zeaxanthin, and their (E/Z)-isomers in the extracts from some of the most commonly consumed fruits, vegetables, and pasta products were determined by HPLC employing a silica-based nitrile-bonded column. Green vegetables had the highest concentration of lutein (L) and zeaxanthin (Z), and the ratios of these carotenoids (L/Z) were in the range 12-63. The yellow-orange fruits and vegetables, with the exception of squash (butternut variety), had much lower levels of lutein in comparison to greens but contained a higher concentration of zeaxanthin. The ratio of lutein to zeaxanthin (L/Z) in two North American bread varieties of wheat (Pioneer, Catoctin) was 11 and 7.6, respectively, while in a green-harvested wheat (Freekeh) imported from Australia, the ratio was 2.5. Between the two pasta products examined, lasagne and egg noodles, the latter had a much higher concentration of lutein and zeaxanthin. The levels of the (E/Z)-geometrical isomers of lutein and zeaxanthin in these foods were also determined. 相似文献
14.
We determined concentrations of Ag, In, Sn, Sb and Bi, and fractionated them by sequential extraction procedures, in five Japanese soils: Andosol‐1 (grassland), Andosol‐2 (forest), Cambisol (forest), Fluvisol (vegetable garden) and Regosol (forest). Average concentrations of Ag, In, Sn, Sb and Bi were 0.17 ± 0.08, 0.081 ± 0.019, 2.2 ± 0.5, 0.83 ± 0.32 and 0.32 ± 0.12 mg kg ?1, respectively. Average distributions of the chemical fractions (omitting those with an abundance < 5%) were: Ag, residual (60%) > H 2O 2‐extractable, organically bound (H 2O 2‐Org) (18%) > metal–organic complex‐bound (Me‐Org) (10%) > amorphous metal oxide‐bound (am‐MeOx) (8.3%); In, residual (61%) > H 2O 2‐Org (12%) > Me‐Org (8.7%) ≥ crystalline Fe oxide‐bound (cr‐FeOx) (8.2%) > am‐MeOx (7.4%); Sn, residual (40%) > Me‐Org (19%) > carbonate‐bound (12%) > cr‐FeOx (9.0%) > H 2O 2‐Org (7.8%) > am‐MeOx (6.9%); Sb, residual (34%) > Me‐Org (18%) > am‐MeOx (16%) > cr‐FeOx (8.9%) ≥ H 2O 2‐Org (8.7%) > easily reducible metal oxide‐bound (re‐MeOx) (6.8%) > carbonate‐bound (6.1%); Bi, am‐MeOx (26%) ≥ H 2O 2‐Org (26%) > Me‐Org (19%) > residual (17%) > cr‐FeOx (12%). Proportions of the mobilizable (exchangeable + carbonate‐bound + Me‐Org + re‐MeOx) metal fractions were in the order Sn ≥ Sb > Bi > Ag ? In, and Cambisol > Andosol‐2 > Regosol > Andosol‐1 > Fluvisol. The proportions were predicted by multiple regression equations including pH, surface area, C contents, cation exchange capacity and clay content of the soils as independent variables ( R2 > 0.96, P < 0.02). 相似文献
15.
Purpose Smelting activity produced tons of slags with large quantities of highly toxic metals, resulting in contamination in adjacent
soils and sediments as well. This study investigated the fractionation and sources of metals Pb, Zn, and Cd in polluted soils
and sediments in a region with once prosperous Zn smelting activities in southwestern China. Soils with varying land uses
were of a special concern due to their connection to the food chain. Obtained data would offer a valuable reference to the
development of land-use management strategy in this region. 相似文献
16.
Perchlorate is an inhibitor of iodide uptake that is found widely in the environment. Given the potential for perchlorate accumulation during egg formation and the widespread consumption of eggs, it is important to examine eggs as a source of exposure to perchlorate and other potential inhibitors of iodide uptake (nitrate and thiocyanate). This study was conducted to determine potential human exposure to perchlorate from eggs produced by chicken flocks consuming differing amounts of perchlorate. The mean concentrations of perchlorate (7.16 ( 1.99 microg/kg of dry weight), nitrate (2820 ( 2100 microg/kg of dry weight), thiocyanate (574 +/- 433 microg/kg of dry weight), and iodide (2980 ( 1490 microg/kg of dry weight) in eggs (n = 180) from 15 chicken houses on 3 U.S. farms were determined. Chickens secreted into eggs an average of 23% of the perchlorate ingested from feed and water. Perchlorate levels in eggs were positively correlated with perchlorate intake (p < 0.001). Increased intake of perchlorate, nitrate, and thiocyanate was associated with decreased iodide levels in eggs, possibly indicating a competitive transport mechanism, such as sodium-iodide symporter. It was estimated that egg consumption contributes minimal perchlorate (approximately 0.040 microg) compared to the average total intake of approximately 10.5 microg for U.S. adults. Additionally, it was found that egg consumption was not associated with increased perchlorate exposure in 2820 individuals from the National Health and Nutrition Examination Survey (p value for the difference of least-squares means, pDiff = 0.225). From these findings it was concluded that, although chickens secrete perchlorate in eggs, eggs do not appear to be a significant source of perchlorate exposure for adults in the United States. 相似文献
17.
Ontogenic variations in N 2 fixation and accumulation of N by the mungbean ( Vigna radiata L. Wilczek), blackgram ( Vigna mungo L. Hepper), cowpea ( Vigna unguiculata L. Walp.), and groundnut ( Arachis hypogaea L.) were studied by a 15N-dilution technique. Pots filled with 7 kg of red yellow podzolic soil were used. Samples were taken 20, 40, 60, and 80 days after emergence which approximately corresponded to preflowering, flowering, early/mid-pod filling and late pod filling stages, respectively. During early growth (up to 40 days after emergence), the carryover of seed N accounted for a considerable fraction of the total plant N in the legumes, the highest being in the groundnut. With a correction for carryover, the groundnut derived over 45% of its N content from the atmosphere 20 days after emergence whereas the corresponding figures were 33% for the blackgram and about 28% for the cowpea and mungbean. Between flowering and early pod fill, there was a rapid increase in N 2 fixation in all legumes except in groundnut which showed highest fixation from 60 to 80 days after emergence. In the mungbean, N 2 fixation and uptake of soil N were insignificant 60 days after emergence while in other legumes these processes continued beyond this time. All legumes derived about 90% of their N from atmosphere by 80 days after emergence. However, due to considerable interspecific differences in total N yield the final amount of N 2 fixed showed an appreciable variation among legumes. It was highest in the groundnut (443 mg N plant -1) followed by the cowpea (385), blackgram (273), and mungbean (145), respectively. The groundnut maintained nodules until the late pod filling stage while in other legumes, nodules senesced progressively following the mid-pod filling stage. During pod filling there was a net mobilization of N from vegetative tissues to developing pods in the mungbean, which amounted to about 20% of N in seeds. This mobilization was not evident in other legumes. 相似文献
18.
Competition and compatibility between livestock and wildlife in Africa has been a point of considerable speculation, with implications for conservation. However, controlled replicated experiments are lacking. Here we report on the results of a long-term exclosure experiment in Laikipia, Kenya, in which different guilds of large mammalian herbivores have been independently manipulated since 1995. In plots from which cattle were excluded, the density of zebra dung in 2000 was on average 46% greater than in control plots. This was due to differential zebra use, and not to differential rates of dung removal (by dung beetles or other factors). Vegetation data indicate that cattle fully compensate for the absence of wildlife; all plots accessible to cattle had similarly low grass cover. However, wildlife do not fully compensate for the absence of cattle; plots with only wildlife had more grass cover than plots accessible to cattle. Zebra dung density was strongly correlated with total grass cover, suggesting that zebras are effectively tracking resource abundance. There is also evidence of pair-wise competition between cattle and elephants, and between elephants and zebras. The strong competition between cattle and zebras appears to be mitigated by the presence of elephants. A significant cattle x elephant interaction on the abundance of zebra dung indicates that elephants reduce the negative effects of cattle on zebras. In the presence of cattle, elephants facilitate the abundance of zebra, apparently by suppressing resource extraction (bite rates) by cattle. The precise mechanism for this indirect facilitation is not clear, but it may be related to the demonstrated reduction in forb cover associated with elephant presence. 相似文献
19.
PurposeWith increasing urban area and population, global cities are playing a more important role in the alteration of the global biogeochemical cycles. The aims of this study are to understand the concentrations and stoichiometric relations of biogenic elements (C, N, and P) in urban soils, further to reveal the effects of C, N, and P accumulation on the urban environment. Materials and methodsWe collected 317 surface (0–10 cm) soil samples taken from Nanjing, China, a typical city with more than 2000 years of history. These soil samples were located in different urban zones of Nanjing with different land use histories. The soil C, N, and P concentrations were determined. The stoichiometric relations of soil C, N, and P were investigated in urban soils. Meanwhile, some studies on sources of C, N, and P in diverse urban settings from literature were combined to explore the universal rule of C, N, and P cycling and their ecological and environmental effects in urban area. Results and discussionCompared to rural soils, more C, N, and P are accumulated in the urban soils, which also change their stoichiometric relations. The concentrations of OC, TN, and TP in urban top soils are 17.0 ± 9.69 g kg?1, 1.53 ± 0.92 g kg?1, and 1.31 ± 0.67 g kg?1, respectively. The mean atomic ratio of C:N:P is 37:3:1 in the surface of urban soils that strictly differs from natural soils in China and the whole world. The mean of C:N ratio in urban soils is similar to that of agriculture, grassland, and forest soils. However, the ratios of C:P and N:P in urban soils are much lower than that in agricultural, forest, and grassland soils. This implies that P is extremely enriched in the urban soils. The high C in urban soils are considered coming from natural and anthropogenic sources. The high N and P mainly come from anthropogenic sources. ConclusionsThe well-constrained C:N:P ratio in rural soils does not apply for urban soils. The abnormal C:N:P ratio of urban soils is the result of unbalanced accumulation of C, N, and P from human activities. Urban soils are already an important storage of carbon. High N and P in urban soils may bring threat of surface water eutrophication and ground water contamination. These effects are expected to increase with the city development time. 相似文献
20.
A study was conducted to determine the presence of resveratrol, pterostilbene, and piceatannol in Vaccinium berries. Samples representing selections and cultivars of 10 species from Mississippi, North Carolina, Oregon, and Canada were analyzed by gas chromatography/mass spectrometry. Resveratrol was found in Vaccinium angustifolium (lowbush blueberry), Vaccinium arboretum (sparkleberry), Vaccinium ashei (rabbiteye blueberry), Vaccinium corymbosum (highbush blueberry), Vaccinium elliottii (Elliott's blueberry), Vaccinium macrocarpon (cranberry), Vaccinium myrtillus (bilberry), Vaccinium stamineum (deerberry), Vaccinium vitis-ideae var. vitis-ideae (lingonberry), and Vaccinium vitis-ideae var. minor (partridgeberry) at levels between 7 and 5884 ng/g dry sample. Lingonberry was found to have the highest content, 5884 ng/g dry sample, comparable to that found in grapes, 6471 ng/g dry sample. Pterostilbene was found in two cultivars of V. ashei and in V. stamineum at levels of 99-520 ng/g dry sample. Piceatannol was found in V. corymbosum and V. stamineum at levels of 138-422 ng/g dry sample. These naturally occurring stilbenes, known to be strong antioxidants and to have cancer chemopreventive activities, will add to the purported health benefits derived from the consumption of these small fruits. 相似文献
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