Bioaccumulation of selenate,selenite, and seleno-DL-methionine by the brine fly larvae Ephydra cinerea Jones

High concentrations of selenium threaten waterfowl at California San Joaquin Valley agricultural wastewater evaporation ponds. This study evaluates and compares two routes of Se exposure and uptake by third instar Ephydra cinerea (brine fly) larvae. A 48-h static bioconcentration bioassay provided information on the larval uptake of selenate, selenite, and seleno-DL-methionine (SeMet) at Se waterborne concentrations ranging from 10.0–20,000 ug/L. At equivalent concentration levels, SeMet was bioconcentrated to a greater extent than selenite, which was bioconcentrated more than selenate. Forty-eight-hour static bioconcentration vs. biomagnification bioassays allowed for comparisons of the two routes of exposure of selenate, selenite, and SeMet. Biomagnification was determined to be the primary Se uptake pathway, exemplified most notably in the selenite treatment. Measured agar-based food unit Se levels presented evidence that the uptake of selenite, and especially SeMet, by microbial populations was transferred to E. cinerea larvae as they scavenged for bacteria and yeast, etc. in the diet matrix. As a primary dietary item of waterfowl at evaporation ponds, E. cinerea in seleniferous waters presents a potentially high hazard.     

The effect of sulfate on the bioconcentration of selenate by Chironomus decorus and Daphnia magna

Agricultural drainage containing high concentrations of selenium (Se) poses a continuing threat to wildlife in California's San Joaquin Valley. Drainage water from this area frequently contains high concentrations of sulfate, which are known to have mediating effects on the bioaccumulation and toxicity of Se in some organisms. It has been proposed that sulfate concentration should be a consideration in determining water quality criteria for Se. As a step toward analyzing the viability of such a plan, this study evaluated the effect of varying sulfate concentration on Se bioconcentration by two aquatic invertebrates. Fourth instar Chironomus decorus and neonate Daphnia magna were exposed, for a 48 h period, to 5.92 and 0.71 mg Se/L, as selenate, respectively. The selenium:sulfur (Se:S) ratio in the dilution waters ranged from 1:0 to 1:480 for C. decorus and 1:3 to 1:240 for D. magna. Increasing sulfate concentrations significantly reduced the accumulation of Se by both organisms. However, D. magna and C. decorus bioconcentrate Se differently at low sulfate concentrations. This difference can be explained by a two permease model for selenate/sulfate absorption. Although this experiment showed that sulfate may reduce selenate bioavailability to aquatic invertebrates, there is no indication that sulfate may completely eliminate selenate absorption. Thus, further research should be performed before sulfate concentration becomes a factor in the determination of water quality standards for selenium.     

Selenium Bioaccumulation by the Water Boatman Trichocorixa reticulata (Guerin-Meneville)

The input of selenium from subsurface agricultural drainage into surface water systems can result in the accumulation of toxic concentrations of selenium in aquatic food chains. Elevated selenium concentrations in aquatic systems is a significant environmental problem in many areas of the United States. A laboratory investigation was conducted to determine the dominant route of selenium bioaccumulation by the corixid Trichocorixa reticulata, an important food chain organism. The roles of waterborne and foodborne exposure in selenium bioaccumulation were examined using 48-h bioassays. Waterborne selenium concentrations ranged from 0 to 1,000 μg Se/L as selenate. A mixture of two species of blue-green algae cultured in media with selenium concentrations ranging from 0 to 1,000 μg Se/L as selenate was used as a corixid diet in the foodborne treatments. Corixids exposed to waterborne selenate did not accumulate selenium above control concentrations. Corixids fed algae exposed to ≥100 μg Se/L as selenate had significantly higher selenium concentrations than control organisms. These data suggest that corixids may be effectively isolated from the water and selenium accumulation is solely through dietary exposure. Received: 8 July 1998/Accepted: 21 October 1998     

The toxicity of waterborne boron toDaphnia magna andChironomus decorus and the effects of water hardness and sulfate on boron toxicity

The concentrations of many elements, including boron, are increasing in aquatic ecosystems due to anthropogenic activities. Laboratory studies were undertaken to evaluate the toxicity of waterborne boron to two key fresh water macroinvertebrates and to evaluate the effects of water hardness and sulfate on boron toxicity. Acute toxicity evaluations of waterborne sodium tetraborate resulted in 48 h. LC₅₀ values of 141 and 1376 mg B/L for neonateDaphnia magna and fourth instarChironomus decorus, respectively. Chronic sublethal studies demonstrated a significant decrease inC. decorus growth rate at 20 mg B/L. Further studies showed that increasing water hardness (10.6 to 170 mg/L as CaCO₃) and sulfate (10.2 to 325.4 mg SO₄ ^–1/L) concentrations did not affect boron toxicity toD. magna. These results, in conjunction with a review of the literature, suggest that aquatic macrophytes may be more sensitive to boron than macroinvertebrates and thus would be better choices for aquatic risk assessment evaluations for this element.     

Toxicity and accumulation of selenite and selenate in the unicellular marine alga Cricosphaera elongata

The toxicity and bioaccumulation of selenium in the 4⁺ and 6⁺ oxidation states were investigated in a marine unicellular alga Cricosphaera elongata in culture. Selenite was more toxic than selenate. Exponentially growing cells and cells in the stationary phase of C. elongata rapidly accumulated selenite (0.1 and 1.0 mg/L Na₂SeO₃) and selenate (0.1 and 1.0 mg/L Na₂SeO₄). Within the first two hours of contact, the amount of selenium taken up decreased sharply in exponentially growing cells, while cells in the stationary phase continued accumulating selenium until a plateau was reached. The presence of metabolic inhibitors such as KCN (potassium cyanide) or DCMU (3-(3,4-dichloro-phenyl)-1,1 dimethylurea) or glutaraldehyde did not modify the first phase of accumulation of selenite by C. elongata in the stationary phase, whereas further accumulation was inhibited. Possible mechanims of accumulation of selenium are discussed. In a series of long term experiments (14 or 31 d), intracellular partitioning of Se in C. elongata cells, exposed to selenite, was analysed; total, protein-bound and free cytosolic selenium concentrations increased with selenium concentration added to the culture medium (0.1 or 1 mg/L Na₂SeO₃) and with exposure time (at 0.1 mg/L Na₂SeO₃) from 14 d or 31 d. Most of the selenium was associated with proteins; these proteins may represent a form of storage or detoxication of selenium.     

Acute toxicity of boron,molybdenum, and selenium to fry of chinook salmon and coho salmon

The acute toxicities of boron, molybdenum, and various forms of selenium, individually and in environmentally relevant mixtures, to swim-up and advanced fry of chinook salmon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch) were determined in site-specific fresh and brackish waters. Boron and molybdenum were relatively non-toxic (96-hr LC50s > 100 mg/L) to both life stages of both species. Selenite was significantly more toxic than selenate to both species. Swim-up fry tested in fresh water were significantly more sensitive than advanced fry in brackish water to selenate and selenite. No mortalities occurred in any concentrations tested of seleno-DL-methionine; however, in the highest concentration (21.6 mg Se/L), at least 50% of the fish showed pronounced surfacing behavior. Coho salmon were more sensitive than chinook salmon to both selenate and selenite at either life stage; only the swim-up fry of coho salmon were more sensitive than chinook salmon to boron. In additional tests with swim-up chinook salmon, differences in the characteristics of the dilution water did not significantly modify the relative toxicities of boron, selenate, and selenite. In binary mixture studies, the joint acute toxic action of selenate and selenite, combined in various ratios, was additive to both species. Based on a comparison of the individual acute values for chinook salmon to the expected environmental concentrations, the margin of safety for boron was only 56 in fresh and 46 in brackish water. The margins of safety for selenate and selenite exceeded 275 in both fresh and brackish waters. However, the margin of safety for both selenate and selenite in the mixture test was 145 in fresh water and 220 in brackish water.     

The antagonism between selenium and cadmium in a freshwater mollusc

The protective effect of selenium against cadmium toxicity in rats is well documented. Data concerning such protection are lacking in invertebrates. The object of this study was to check whether such an antagonism between Se and Cd can be found in the freshwater molluscLymnaea stagnalis L. In the presence of sublethal amounts of selenium, sensitivity with respect to cadmium is nearly halved. Sublethal amounts of cadmium give additional protection against the toxic effects of selenium, since this concentration completely prevented mortality due to high doses of selenite (3 mg/L Se) and selenate (15 mg/L Se).     

Selenium bioaccumulation in aquatic ecosystems: 1. Effects of sulfate on the uptake and toxicity of selenate in Daphnia magna

Selenium contamination and toxicity have been reported for aquatic ecosystems across the United States. Because waterborne selenium concentrations in natural systems are seldom high enough to be directly toxic, it has been concluded that bioaccumulation of selenium is causing observed toxicity problems. As a result, information regarding the bioaccumulation processes of selenium in aquatic organisms is necessary for appropriate management and remediation of selenium in aquatic ecosystems. Studies of selenium bioaccumulation in bacteria, fungi, and algae have indicated that selenate and sulfate compete for uptake via a common mechanism. However, such competitive interactions have not been examined in higher, multi-cellular organisms. To address this, we conducted experiments to determine how changes in ambient sulfate concentrations affect the uptake of selenate in the freshwater crustacean Daphnia magna. D. magna were exposed to waterborne selenate concentrations ranging from control to 500 g/L Se with varying concentrations of sulfate ranging from 0 mg/L to concentrations equivalent to EPA very hard water. At the higher concentrations of selenate, selenium uptake increased significantly as sulfate concentrations decreased. No toxicity was observed except at the 500 g/L Se and no sulfate treatment, where virtually all of the daphnids died within 72 h.     

The toxicity and bioaccumulation of selenate,selenite and seleno-L-methionine in the cyanobacteriumAnabaena flos-aquae

A laboratory investigation was conducted to study the toxicity and bioaccumulation of seleno-L-methionine, selenate and selenite in the cyanobacteriumAnabaena flos-aquae. The first sub-lethal effects of seleno-L-methionine, selenite and selenate occurred at 0.1, 3.0, and 3.0 mg/L, respectively with a decrease in chlorophylla concentration (P < 0.0001). Selenium bioconcentration factors (BCF) were in the order of seleno-L-methionine, selenite, and selenate. Significant decreases in intracellular selenium concentration were observed at both the no effect (NOEL) and low effect levels (LOEL) at each oxidation state tested in the given experiment (p < 0.0001). Mechanisms for the assimilation, toxicity and regulation of selenium are presented.     

The Toxicity of Glyphosate and Several Glyphosate Formulations to Four Species of Southwestern Australian Frogs

The acute toxicity of technical-grade glyphosate acid, glyphosate isopropylamine, and three glyphosate formulations was determined for adults of one species and tadpoles of four species of southwestern Australian frogs in 48-h static/renewal tests. The 48-h LC₅₀ values for Roundup? Herbicide (MON 2139) tested against tadpoles of Crinia insignifera, Heleioporus eyrei, Limnodynastes dorsalis, and Litoria moorei ranged between 8.1 and 32.2 mg/L (2.9 and 11.6 mg/L glyphosate acid equivalent [AE]), while the 48-h LC₅₀ values for Roundup? Herbicide tested against adult and newly metamorphosed C. insignifera ranged from 137–144 mg/L (49.4–51.8 mg/L AE). Touchdown? Herbicide (4 LC-E) tested against tadpoles of C. insignifera, H. eyrei, L. dorsalis, and L. moorei was slightly less toxic than Roundup? with 48-h LC₅₀ values ranging between 27.3 and 48.7 mg/L (9.0 and 16.1 mg/L AE). Roundup? Biactive (MON 77920) was practically nontoxic to tadpoles of the same four species producing 48-h LC₅₀ values of 911 mg/L (328 mg/L AE) for L. moorei and >1,000 mg/L (>360mg/L AE) for C. insignifera, H. eyrei, and L. dorsalis. Glyphosate isopropylamine was practically nontoxic, producing no mortality among tadpoles of any of the four species over 48 h, at concentrations between 503 and 684 mg/L (343 and 466 mg/L AE). The toxicity of technical-grade glyphosate acid (48-h LC₅₀, 81.2–121 mg/L) is likely to be due to acid intolerance. Slight differences in species sensitivity were evident, with L. moorei tadpoles showing greater sensitivity than tadpoles of the other four species. Adult and newly emergent metamorphs were less sensitive than tadpoles. Received: 19 February 1998/Accepted: 16 August 1998     

Toxicity of Select Beta Adrenergic Receptor-Blocking Pharmaceuticals (B-Blockers) on Aquatic Organisms

One class of pharmaceutical compounds identified in U.S. and European waters are the B-adrenergic receptor blocking compounds (B-blockers). However, little information is available on the potential aquatic toxicity of these compounds. Therefore, Hyalella azteca, Daphnia magna, Ceriodaphnia dubia, and Oryias latipes (Japanese medaka) were exposed to metoprolol, nadolol, and propranolol to determine potential toxicity. Average 48-h LC₅₀ for propranolol to H. azteca was 29.8 mg/L. The no-observed-effects concentration (NOEC) and lowest-observed-effects concentration (LOEC) for propranolol affecting reproduction of H. azteca were 0.001 and 0.1 mg/L, respectively. The average propranolol and metoprolol 48-h LC₅₀s for D. magna were 1.6 and 63.9 mg/L, respectively. C. dubia 48-h LC₅₀s were 0.85 and 8.8 mg/L for propranolol and metoprolol, respectively. The NOEC and LOEC of propranolol affecting reproduction in C. dubia were 0.125 and 0.25 mg/L, respectively. In O. latipes, the propranolol 48-h LC₅₀ was 24.3 mg/L. Medaka growth was decreased at 0.5 mg/L propranolol. A 2-week medaka reproductive study indicated significant changes in plasma steroid levels; however, no changes in the average number of eggs produced or number of viable eggs which hatched was observed. In a 4-week follow-up propranolol exposure, the total number of eggs produced by medaka and the number of viable eggs that hatched were decreased at concentrations as low as 0.5 μg/L. Based on this study and the expected aqueous environmental exposure levels, adverse effects of propranolol to invertebrate populations is unlikely; however, further reproductive studies are need to elucidate the risk to teleosts. Received: 14 August 2001/Accepted: 4 March 2002     

Comparison of Selenium Toxicity in Sunflower and Maize Seedlings Grown in Hydroponic Cultures

Several studies have demonstrated that selenium (Se) at low concentrations is beneficial, whereas high Se concentrations can induce toxicity. Controlling Se uptake, metabolism, translocation and accumulation in plants is important to decrease potential health risks and helping to select proper biofortification methods to improve the nutritional content of plant-based foods. The uptake and distribution of Se, changes in Se content, and effects of various concentrations of Se in two forms (sodium selenite and sodium selenate) on sunflower and maize plants were measured in nutrient solution experiments. Results revealed the Se content in shoots and roots of both sunflower and maize plants significantly increased as the Se level increased. In this study, the highest exposure concentrations (30 and 90 mg/L, respectively) caused toxicity in both sunflower and maize. While both Se forms damaged and inhibited plant growth, each behaved differently, as toxicity due to selenite was observed more than in the selenate treatments. Sunflower demonstrated a high Se accumulation capacity, with higher translocation of selenate from roots to shoots compared with selenite. Since in seleniferous soils, a high change in plants’ capability exists to uptake Se from these soils and also most of the cultivated crop plants have a bit tolerance to high Se levels, distinction of plants with different Se tolerance is important. This study has tried to discuss about it.     

Toxicity of selenomethionine- and seleno-contaminated sediment to the amphipod Corophium sp

The acute toxicity of four chemical species of selenium to juvenile amphipods (Corophium sp.) was assessed in water-only tests. The seleno-amino acid compounds seleno-L-methionine and seleno-DL-cystine were found to be more toxic (96-h LC(50) values of 1.5 and 12.7 microg Se/L) than the inorganic selenite and selenate (96-h NOEC values of 58 and 116 microg Se/L). New marine sediment testing procedures were developed using juvenile and adult Corophium sp. Both life stages were highly sensitive to seleno-L-methionine-spiked sediment. The juveniles were approximately five times more sensitive, with a 10-day LC(50) of 1.6 microg Se/g (dry weight) compared to 7.6 microg Se/g (dry weight) for the adults. Sediment collected from three sites in Lake Macquarie, a marine barrier lagoon with elevated concentrations of total selenium, had no effect on the survival of adult Corophium over 10 days. The toxicity of seleno-L-methionine to other amphipod species occurring in Lake Macquarie was assessed in water-only tests, with Paracalliope australis being highly sensitive (96-h LC(50) 2.58 microg Se/L).     

Bioaccumulation and toxicity of selenium in Chironomus decorus larvae fed a diet of seleniferous Selenastrum capricornutum

The bioaccumulation and toxicity of selenium in a simple aquatic food chain was investigated by feeding a diet of seleniferous algae (Selenastrum capricornutum) to fourth instar midge (Chironomus decorus) larvae. Treatment diets consisted of S. capricornutum cultured in three concentrations of selenite (0, 10, and 40 g Se/L) and four concentrations of selenate (0, 4, 10, and 40 g Se/L). The seleniferous algae was freeze-dried and utilized as a diet for the midge larvae. The data show that, under laboratory conditions, a 96 h dietary exposure of 2.11 g Se/g dry weight significantly reduced larval growth at tissue concentrations 2.55 g Se/g dry weight. The results demonstrate that some invertebrates are very sensitive to dietary selenium exposure. When compared to similar studies with Daphnia magna, the data suggest that invertebrate primary consumers differ in the metabolism of dietary selenium.     

Toxicity of Un-ionized Ammonia,Nitrite, and Nitrate to Juvenile Bay Scallops, <Emphasis Type="Italic">Argopecten irradians irradians</Emphasis>

Juvenile bay scallops (7.2–26.4 mm) were exposed for 72 h to different concentrations of un-ionized ammonia, nitrite, or nitrate. Using the Trimmed Spearman Karber method, 50% lethal concentrations (LC₅₀) and 95% confidence limits were calculated individually for each. Un-ionized ammonia concentrations above 1.0 mg N-NH₃/L resulted in 100% scallop mortality within 72 h. The 72-h LC₅₀ for un-ionized ammonia was calculated at 0.43 mg N/L. At nitrite concentrations of 800 mg N/L or higher 100% mortality was observed. The 72-h LC₅₀ for nitrite was calculated at 345 mg N/L. Nitrate was the least toxic, with 100% mortality observed at a concentration of 5000 mg N/L. The calculated nitrate 72-h LC₅₀ was 4453 mg N/L. Our results indicate that un-ionized ammonia is the most lethal nitrogenous waste component to bay scallops.     

Selenium uptake by larval Chironomus decorus from a Ruppia maritima-based benthic/detrital substrate

Elevated levels of selenium have led to the contamination of several aquatic ecosystems. Much of the selenium contamination has resulted from agricultural irrigation and drainage of seleniferous soils. Disposal of selenium contaminated drainwater in evaporation ponds has led to selenium bioaccumulation and toxicity in waterfowl and shorebirds using these ponds. Studies have demonstrated that it is a seleno-amino acid that causes the observed toxicity. However, selenate is the dominant form of selenium in agricultural drainwater, and the biotransformation of selenate into seleno-amino acids has been shown to be greatly limited relative to the more reduced selenium species. We hypothesize that it is in the benthic zone, where the reducing environment facilitates conversion of selenate to selenium forms more conducive to biotransformation, that most biotransformation and subsequent bioaccumulation of seleno-amino acids takes place, and that movement of selenium into the benthic-detrital food chain is a key pathway leading to selenium bioaccumulation. This hypothesis was investigated by conducting laboratory benthic-detrital food chain experiments using the common evaporation pond macrophyte Ruppia maritima as the benthic-detrital substrate. Larval Chironomus decorus were reared on the contaminated Ruppia substrate, and the resulting bioaccumulation and toxicity in the larvae were determined.     

Comparative toxicity of selenite and selenate to the amphipodHyalella azteca

Selenium contamination of aquatic ecosystems is rapidly becoming a concern throughout the United States, leading to a lowering of the freshwater selenium criteria by the U.S. Environmental Protection Agency from 35 g/L to 5 g/L measured as total selenium. However, considerable information indicates important differences in bioaccumulation and toxicity between the various selenium forms. We conducted a series of experiments to determine the comparative toxicity of selenite and selenate to the amphipodHyallela azteca. In 48 h, 96 h, and 240 h (10 d) LC50 tests, selenite was 2 to 4 times more toxic than selenate, the difference decreasing as exposure time increased. This difference in toxicity was even more pronounced in the 24 d reproductive bioassay, where selenite caused a significant decrease in number of young per female at 200 g/L while selenate had no effect up through 700 g/L (the highest concentration tested).     

Biofortification with selenium and implications in the absorption of macronutrients in Raphanus sativus L.

It is well known that selenium (Se) is an essential element for humans, presenting antioxidant functions. This study aimed to evaluate the efficiency of Raphanus sativus L. as an agricultural crop indicated for selenium biofortification and to investigate the influence of different sources and forms of application on Se accumulation and macronutrient absorption. The experiment followed a randomized complete design with five replicates, arranged in a 2 × 2 + 1 factorial scheme, consisting of two sources of Se (sodium selenate and sodium selenite) and two forms of application (application in the soil at the dose of 1.2 mg kg⁻¹ of Se and foliar application at the dose of 50 μmol L⁻¹ of Se), with a control treatment without the addition of selenium. The accumulations of Se in the leaf, root, and whole plants were higher with the selenate source applied via soil when compared with the foliar application. For the selenite source applied via soil, Se root contents were higher when compared with the fertilization via leaf. The Se content in the root was lower for the selenate applied via soil when compared with the other treatments and the control. Raphanus sativus L is an agricultural crop suitable for the agronomic biofortification of selenium, since it concentrates the appropriate levels of Se in the roots and leaves, not harming the crop yield. The application of Se in the form of selenate and via soil was the best technique to increase the contents of Se in the plant, without causing damages in the accumulation of biomass, despite having led to a reduction in the accumulation of S.     

Selenium bioaccumulation in Chlamydomonas reinhardtii and subsequent transfer to Corbicula fluminea: role of selenium speciation and bivalve ventilation

The uptake of Se by the freshwater alga Chlamydomonas reinhardtii and the subsequent transfer to the Asiatic clam Corbicula fluminea was investigated. The objective was to investigate the bioavailability of algal-bound Se for C. fluminea while taking into account Se speciation and bivalve ventilation. First, uptake rates of waterborne Se (selenite, selenate, and selenomethionine) in the algae during a 1-h exposure period were determined for a range of concentrations up to 2,000 microg/L. Fluxes for selenite uptake were constant in the range of concentrations tested, whereas fluxes for selenate and selenomethionine uptake decreased with increasing concentrations, suggesting a saturated transport system at high concentrations (approximately 1,000 microg/L for selenate and 100 microg/L for selenomethionine). These data were used to set the algal contamination for the study of trophic transfer to the clam. Three parameters were studied: The Se form, the algal density, and the Se burden in the algae. The results show that for a fixed algal density, an Se-contaminated algal diet does not modify ventilation. In this case, the driving factor for ventilation is the algal density, with ventilation being enhanced for low algal densities. On the basis of ventilatory flow rate measurements and Se burdens in algae, it was found that bioaccumulation of Se in C. fluminea was proportional to the total quantity of Se passing through the whole organism, but with a lesser extraction coefficient for selenomethionine than for the inorganic forms. These results underline the importance of both physiological factors and speciation in understanding the trophic transfer of Se.     

Toxicity and oxidative stress of different forms of organic selenium and dietary protein in mallard ducklings

Concentrations of over 100 ppm (mg/kg) selenium (Se) have been found in aquatic plants and insects associated with irrigation drainwater and toxicity to fish and wildlife. Composition of diet for wild ducklings can vary in selenium-contaminated environments. Earlier studies have compared toxicities and oxidative stress of Se as selenite to those of seleno-DL-methionine (DL) in mallards (Anas platyrhynchos). This study compares DL, seleno-L-methionine (L), selenized yeast (Y) and selenized wheat (W). Day-old mallard ducklings received an untreated diet (controls) containing 75% wheat (22% protein) or the same diet containing 15 or 30 ppm Se in the above forms except for 30 ppm Se as W. After 2 weeks, blood and liver samples were collected for biochemical assays and Se analysis. All forms of selenium caused significant increases in plasma and hepatic glutathione peroxidase activities. Se as L at 30 ppm in the diet was the most toxic form, resulting in high mortality (64%) and impaired growth (>50%) in survivors and the greatest increase in ratio of oxidized to reduced hepatic glutathione (GSH). Se as both L and DL decreased the concentrations of hepatic GSH and total thiols. Se as Y accumulated the least in liver (approximately 50% of other forms) and had less effect on GSH and total thiols. In a second experiment, in which the basal diet was a commercial duck feed (22% protein), survival was not affected by 30 ppm Se as DL, L, or Y and oxidative effects on GSH metabolism were less pronounced than with the wheat diet.