The control of boron accumulation by two genotypes of wheat

The mechanism of boron (B) uptake in wheat was studied using two genotypes with known differences in their ability to accumulate B. Influx and efflux of B was measured in the roots of intact 21 d old plants.Roots grown in 15 M B, when transferred to solutions containing 1mM B showed a rapid increase in B content for up to 60 min, after which no further increase was evident up to 4 h. No genotypic difference in B influx was apparent over these time periods. Roots grown in 1mM B for 7 d and then rinsed in B-free solutions quickly lost most of B that they contained within 1 hour; little further efflux was observed over the following three hours. As with the influx, no genotypic difference in B flux was evident.It is suggested that the lack of genotypic difference in the short-term B fluxes could be due to a masking effect of extracellular B bound in the cell walls of the roots.Department of Botany, University of Adelaide     

Plasma and liver selenium levels in the rat during supplementation with 0.5, 2, 6, and 15 ppm selenium in drinking water

Plasma and liver selenium of Wistar rats were determined after 1, 3, and 6 mo supplementation with 0.5, 2, 6, or 15 ppm selenium as sodium selenite in drinking water. Plasma selenium was not different from control values at additional intake of 0.5 ppm but increased above usual levels at higher intakes. A highly significant correlation was observed between the total quantity of selenium ingested and plasma selenium after 1 mo treatment (r=0.99,p<0.01), but was less pronounced after 3 and 6 mo (0.94,p<0.05, and 0.78,p<0.05, respectively). The decrease in plasma selenium with time of treatment was more pronounced at higher intakes. There was also a highly significant correlation between total selenium intake and liver selenium concentration (r=0.99,p<0.01) after 1 mo of treatment, but this time liver selenium did not change with time, and the correlation remained highly significant throughout the investigation. Liver selenium therefore appears as a more sensitive and more representative measure of selenium intake than plasma selenium. Most supplements did not affect body weight and survival of animals, except when the diet was supplemented with 15 ppm for 6 mo; however, alterations in biochemical parameters concerning lipid status and hepatic function were observed at levels above 2.0 ppm.     

Sediment toxicity in the Kattegat and Skagerrak

Sediments were sampled from 62 sites in the Kattegat and Skagerrak, which are located between the Baltic and the North Sea in the Western Atlantic, during autumn 1989 and spring 1990. From each site 5 to 6 samples were taken wit ha box-corer. After mixing to composite samples on board, transport and storage (at 4 °C for 2 to 4 weeks), the samples were tested for toxicity to Daphnia magna and Nitocra spinipes. Immobility in Daphnia after exposure to 16 percent sediment (wet wt) in reconstituted standardized water (ISO, 1982) ranged from 0 to 88 percent after 24 h and from 3 to 95 percent after 48 h. For Nitocra the toxicity, determined as the 96-h LC50 (% wet wt) at 7 salinity, ranged from > > 32 percent (nontoxic) to 1.8 percent (most toxic). All exposures were made in duplicates and the effects obtained in the duplicates with the same sediment were correlated to each other. However, sediment toxicity to Daphnia and Nitocra was not. The test with Nitocra, which was made at several concentrations of sediment, was considered to give the most reliable picture of sediment toxicity in the Kattegat and Skagerrak. This ambient toxicity assessment identified three areas with toxic sediment, (1) the Göta älv estuary (outside the city of Göteborg) and its surroundings, (2) the Bay of Laholm in southern Kattegat, which is an area with periodic oxygen depletion and where repeated mussel kills have occurred during the last decade, and (3) an area in the open Skagerrak northwest of Skagen (the tip of the Jutland peninsula). Sediments, which had been stored at 4 °C, were tested again after 6 to 13 mos with the Nitocra test. Stored sediment toxicity was poorly correlated with fresh sediment toxicity. The average detoxification during storage was 5 times, but the range was 3 orders of magnitude, from 17 times more toxic to 73 times less toxic. The reasons for the observed areal and storage differences in sediment toxicity are so far not understood.     

A new approach for testing contaminated marine sediments: fertilization success of lugworms following parental exposure

A sediment bioassay is being developed using several marine benthic invertebrates to assess the effects of parental transfer of contaminants to the gametes. In this preliminary study, the emphasis was placed on developing methods for the in vitro fertilization of lugworm, Arenicola marina, oocytes.Lugworms exposed to contaminated sediments in outdoor mesocosms were brought to the laboratory, just before the beginning of the spawning period. The reliability of an in vitro fertilization procedure was tested by varying several parts of the method. Main results are that eggs and embryos may be physically damaged by cleaning over a sieve. However, as no negative effects were observed when leaving eggs and sperm together for 24 h, the sperm need not be washed off until the embryos are preserved for further examination later on.A first, incomplete screening of the effects of contaminated harbour dredged sediments indicated some effect on the reproductive success.     

Sediment toxicity and heavy metals in the Kattegat and Skaggerak

Superficial (0 to 2 cm) sediments were sampled from 62 sites in Kattegat and Skagerrak during autumn 1989 and spring 1990, tested for toxicity to Daphnia magna and Nitocra spinipes (Crustacea) and analyzed for heavy metals (Cd, Cr, Cu, Hg, N, Pb, Zn), nutrients (N and P) and organic carbon. Whole sediment toxicity to Nitocra spinipes, expressed as 96-h LC50, ranged from 1.8 to > > 32 percent sediment (wet wt), which is equivalent to 0.63 to 53 percent dry wt. Sediment total metal concentrations (mg kg^-1 dry wt) ranged from 0.01 to 0.32 for Cd, 8 to 57 for Cr, 3 to 40 for Cu, 0.03 to 0.86 for Hg, 3 to 43 for Ni, 6 to 37 for Pb and 21 to 156 for Zn. Analyzed concentrations of heavy metals were tested for correlation with whole sediment toxicity normalized to dry wt, and significant correlations (Spearman p<0.05) were found for Cd, Cr, Cu, Hg, and Ni. However, the analyzed concentrations of these metals were below the spiked sediment toxicity of these heavy metals to N. spinipes, except for Cr and Zn for which analyzed maximum concentrations approached the 96-h spiked sediment LC50s. There was no improvement in correlation between the sum of heavy metal concentrations normalized to their spiked toxic concentrations (Toxic Unit approach) and the whole sediment toxicity. Calculated heavy-metal-derived toxicity based on toxic units and whole sediment toxicity ranged from 0.1 to 24 (mean value 2.3 and SD 4.2). Theoretically, a value of 1.0 would explain whole sediment toxicity from measured metal concentrations using this approach. Thus, in spite of the fact that the total concentrations of the heavy metals were sufficient to cause toxicity based on an additive model for most of these sediments, the observed toxicity of the sediments from Kattegat and Skagerrak could not exclusively be explained by the concentrations of heavy metals, except for Cr and Zn at their maximum concentrations. Therefore, other pollutants than these heavy metals must also be considered as possible sediment toxicants.     

Altered free calcium transients in pig kidney cells (LLC-PK1) cultured with penicillin/streptomycin

Summary The effect of a conventional antibiotic (penicillin/streptomycin) mixture on the widely used kidney epithelial cell line, LLC-PK₁, was investigated by measuring growth and intracellular free calcium. Free calcium concentration was the same in cells cultured for 3 to 7 wk with (“plus”) and without (“minus”) antibiotics both at rest and when challenged with high (14 mM) external calcium. When exposed to vasopressin, minus cells exhibited significantly smaller calcium transients than plus cells. A similar difference existed for transients elicited by a calcium ionophore, 4-br-A23187. After longer periods of culture (>20 wk), minus cells grew slower than plus cells but on reaching confluence (minus cells took 1 day longer) the morphologies and viabilities were indistinguishable. The finding that culture with penicillin/streptomycin reversibly modified some properties of LLC-PK₁ cells, at least partly through altered calcium homeostasis, is of importance for workers using this cell model to study drug effects and raises the general possibility of similar effects on other cultured cells.     

Chronic toxicity of ammonia to juvenile gilthead seabream Sparus aurata and related histopathological effects

Effect of 20 days exposure of juvenile gilthead seabream ( Sparus aurata ) to elevated levels of ammonia on growth and survival was examined in a continuous flow system. Suppressed growth and reduced survival were observed at concentrations of 8.2 and 13 mg l⁻¹ total ammonia-N (0.5 and 0.7 mg l⁻¹ un-ionized ammonia-N, respectively) and higher. The maximum acceptable toxic concentration (MATC) for growth was between 4.8 to 8.2 mg l⁻¹ total ammonia-N (0.3 and 0.5 mg l⁻¹ un-ionized ammonia-N, respectively). Fish exposed to high ammonia levels (13 mg l⁻¹ total ammonia-N, 0.7 mg l⁻¹ un-ionized ammonia-N) displayed clear signs of liver pathology. Existing evidence suggests that S. aurata is less sensitive to ammonia than other reported marine and freshwater fish.
Under certain conditions ammonia concentration in the intensive fish ponds in Eilat may exceed the no observed effect concentration for S. aurata .     

Protein toxicity to aphids: Anin vitro test onAcyrthosiphon pisum

Recent progress in plant transformation for insect resistance has increased the interest in the potential toxicity of proteins towards insect pests. While studies have been targeted to a large array of insect species, phloem-feeding Homoptera have not been investigated yet. The paper describes a routine test for screening toxicity and growth inhibition of purified proteins in artificial diets onAcyrthosiphon pisum (Harris). Twenty-five commercially available proteins of different classes were tested and compared to some non-protein chemicals (an insecticide, an antibiotic …).A. pisum proved to be very sensitive to all proteases tested and to some venoms with general cytolytic properties. A plant lectin, concanavalin A, displayed significant toxicity and growth inhibition, while various proteins such as a soybean proteinase inhibitor, a chitinase, and bovine serum albumin showed measurable impairments of growth only at higher dose (≥250 μg.ml⁻¹). Some proteins were without short-term effect onA. pisum physiology. The influence of these results on aphid-plant interactions are discussed.

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Résumé L'effet de protéines alimentaires sur les insectes phloémophages, dont les pucerons, n'a jamais été étudié. Nous proposons ici un test biologique standardisé sur milieu artificiel permettant d'analyser les effets de différentes classes de protéines sur la physiologie d'A. pisum. La validité de ce test est éprouvée (protocole, reproductibilité) et les différentes données récoltées (mortalité et inhibition de croissance) permettent de définir des paramètres toxicologiques tels que concentration létale 50 ou concentration inhibitrice 50. Cette caractérisation toxicologique a été réalisée sur 25 protéines appartenant à des classes différentes, ainsi que plusieurs substances non protéiques utilisées comme témoin de toxicité (insecticide, antibiotique, inhibiteur de synthèse protéique et glucoside phénolique). Les regroupements de protéines par proximités de profils toxicologiques ont été corrélés aux activités biochimiques des différentes protéines. Les implications de ces résultats sur les interactions plante-puceron sont discutées, ainsi que le potentiel d'une stratégie de création de variétés transgéniques résistantes aux pucerons.

     

Al3+-Ca2+ interactions in aluminum rhizotoxicity

Several mineral rhizotoxicities, including those induced by Al³⁺, H⁺, and Na⁺, can be relieved by elevated Ca²⁺ in the rooting medium. This leads to the hypothesis that the toxic cations displace Ca²⁺ from transport channels or surface ligands that must be occupied by Ca²⁺ in order for root elongation to occur. In this study with wheat (Triticum aestivum L.) seedlings, we have determined, in the case of Al³⁺, that (i) Ca²⁺, Mg²⁺, and Sr²⁺ are equally ameliorative, (ii) that root elongation does not increase as Ca²⁺ replaces Mg²⁺ or Sr²⁺ in the rooting media, and (iii) that rhizotoxicity is a function solely of Al³⁺ activity at the root-cell membrane surface as computed by a Gouy-Chapman-Stern model. The rhizotoxicity was indifferent to the computed membrane-surface Ca²⁺ activity. The rhizotoxicity induced by high levels of tris(ethylenediamine)cobaltic ion (TEC³⁺), in contrast to Al³⁺, was specifically relieved by Ca²⁺ at the membrane surface. The rhizotoxicity induced by H⁺ exhibited a weak specific response to Ca²⁺ at the membrane surface. We conclude that the Ca²⁺-displacement hypothesis fails in the case of Al³⁺ rhizotoxicity and that amelioration by cations (including monovalent cations) occurs because of decreased membrane-surface negativity and the consequent decrease in the membrane-surface activity of Al³⁺. However, TEC³⁺, but not Al³⁺, may be toxic because it inhibits Ca²⁺ uptake. The nature of the specific H⁺-Ca²⁺ interaction is uncertain.Abbreviations {Al³⁺ }₀ chemical activity of Al³⁺ at the root-cell membrane surface - {Al³⁺ }_E chemical activity of Al³⁺ in the external rooting medium - E₀ electrical potential at the root-cell membrane surface - HXM²⁺ hexamethonium ion - TEC³⁺ tris(ethylenediamine)cobaltic ion     

Bisphenol S induces oxidative stress-mediated impairment of testosterone synthesis by inhibiting the Nrf2/HO-1 signaling pathway

Bisphenol S (BPS) is an environmental endocrine disruptor widely used in industrial production. BPS induces oxidative stress and exhibits male reproductive toxicity in mice, but the mechanisms by which BPS impairs steroid hormone synthesis are not fully understood. Nuclear factor erythroid 2-related factor 2(Nrf2)/HO-1 signaling is a key pathway in improving cellular antioxidant defense capacities. Therefore, this study explored the effects of exposure to BPS on testosterone synthesis in adult male mice and its mechanisms with regard to the Nrf2/HO-1 signaling pathway. Adult male C57BL/6 mice were orally exposed to BPS (2, 20, and 200 mg/kg BW) with sesame oil as a vehicle (0.1 ml/10 g BW) per day for 28 consecutive days. The results showed that compared with the control group, serum testosterone levels were substantially reduced in the 20 and 200 mg/kg BPS treatment groups, and testicular testosterone levels were reduced in all BPS treatment groups. These changes were accompanied by a prominent decrease in the expression levels of testosterone synthesis-related enzymes (STAR, CYP11A1, CYP17A1, HSD3B1, and HSD17B3) in the mouse testis. In addition, BPS induced oxidative stress in the testis by upregulating the messenger RNA and protein levels of Keap1 and downregulating the levels of Nrf2, HO-1, and downstream antioxidant enzymes (CAT, SOD1, and Gpx4). In summary, our results indicate that exposure of adult male mice to BPS can inhibit Nrf2/HO-1 signaling and antioxidant enzyme activity, which induces oxidative stress and thereby may impair testosterone synthesis in testicular tissues, leading to reproductive damage.