非离子氨和亚硝酸氮对虾虎鱼仔鱼的急性毒性及安全浓度评价

目的检测非离子氨和亚硝酸氮对鱼类的生态毒性效应。方法在水温（25±1）℃、溶氧（6.07～6.77）mg/L、盐度30～31、pH8.0～8.2的条件下,采用半静水式生物毒性试验方法研究了非离子氨和亚硝酸氮对裸项栉虾虎鱼（Ctenogobius gymnauchen）仔鱼的急性毒性效应（非离子氨浓度梯度设置为0、0.413、0.735、1.309、2.329、4.147 mg/L,亚硝酸氮浓度梯度设置为0、3.0、4.14、5.713、7.884、10.88 g/L）。结果非离子氨和亚硝酸氮暴露后仔鱼出现呆滞、侧游、呼吸困难、体色变白、身体弯曲等中毒症状,且随着暴露浓度的升高与暴露时间的延长,死亡率逐渐增加,存在明显的剂量效应关系和时间效应关系;非离子氨和亚硝酸氮对裸项栉虾虎鱼仔鱼96 hLC50分别为9.1 mg/L和12.405 g/L,其安全浓度分别为0.91 mg/L和1.2405 g/L。结论裸项栉虾虎鱼对非离子氨和亚硝酸氮具有较强的耐受力,非离子氨对裸项栉虾虎鱼仔鱼的毒性显著大于亚硝酸氮。     

Influence of aluminum in nutrient solutions on chemical composition in upland rice cultivars

Summary Aluminum toxicity is an important growth limiting factor for upland rice production on oxisols of cerrado region in Brazil. Data related to the effect of Al on uptake of nutrients for rice crop are limited. The effect of five Al concentrations (0, 10, 20, 40 and 60 ppm) in culture solution on the chemical composition of 30 upland rice cultivars was studied.Aluminum concentration and content in plant tissues were increased with higher levels of Al in all cultivar. In the roots Al content was higher as compared with the tops. Critical toxic level of Al in the tops of 21 days old plants varied from 100 to 417 ppm depending on the cultivars. Rice cultivars responded differently to Al treatments with respect to nutrients uptake. Increased Al concentrations in the solution exerted an inhibiting effect on the concentrations and contents of N, P, K, Ca, Mg, S, Na, Zn, Fe, Mn, B and Cu. Thus the inhibition was more effective for macronutrients in the plant tops in following order: Mg>Ca>P>K>N>S>Na. Whereas for micronutrients it was in the order of Mn>Zn>Fe>Cu>B. Morphological, physiological and biochemical effects of Al, toxicity responsible for the reduction in plant nutrient uptake, are discussed.     

Measurement of Free Radicals from Smoke Inhalation and Oxygen Exposure by Spin Trapping and Esr Spectroscopy

Research in smoke inhalation has established that free radicals are produced from gases released during combustion and these species impair lung function. Using spin traps and their adducts in an animal model free radicals were measured. Various hyperbaric oxygen regimens were tested in an attempt to attenuate pulmonary damage caused by free radical reactions. Our data demonstrated that persistent oxygen- and carbon-centered free radicals are detectable in intravascular fluids after smoke inhalation. The smoke inhalation model showed however, clearing of spin trap adducts one hour after smoke exposure. Other researchers have found that when 100% oxygen is given at 1 atmosphere absolute (ATA) for 1 h, free radicals were not detectable. However, oxygen given at 2.5 ATA does produce detectable free radicals. With continued exposure at this pressure, the levels of free radicals increase for up to 60min. This study suggests that the level of free radical induced oxygen toxicity may be a function of oxygen pressure and duration of oxygen exposure.     

The role of calcium in salt toxicity

Salt toxicity comprises osmotic and ionic components both of which can severely affect root and shoot growth. Uptake of Na⁺ across the plasma membrane is very fast resulting in physiological effects on extracellular as well as intracellular sites. Sodium reduces binding of Ca²⁺ to the plasma membrane, inhibits influx while increasing efflux of Ca²⁺, and depletes the internal stores of Ca²⁺ from endomembranes. These changes in the cell Ca²⁺ homeostasis are suggested here to be the primary responses to salt stress that are perceived by root cells. Salt would almost instantly reduce the amount of Ca²⁺ being transferred to the leaf cells, with Ca²⁺ activity dropping and Na⁺ activity rising in the apoplasm of leaf cells. This Ca²⁺ signal would be transported to leaves together with, if not preceding, the signal of limited water supply. Hormonal signals are likely to be secondary in nature and caused by the Na⁺-related disturbance of the root cell Ca²⁺ homeostasis. Ameliorative effects of supplemental Ca²⁺ on salt stress are exerted through preventing Na⁺-related changes in the cell Ca²⁺ homeostasis.     

Heavy metals, lipid peroxidation, and ciguatera toxicity in the liver of the caribbean barracuda (Sphyraena barracuda)

Human consumption of over 400 species of tropical fish containing polyether toxins (e.g. ciguatoxins, maitotoxins) causes ciguatera fish poisoning. The Caribbean barracuda (Sphyraena barracuda) is one of the most potent ciguatoxic fish. The objective of this study was to determine whether toxicity of 14 barracuda livers was correlated with lipid peroxidation. A significant correlation (p = 0.015, Pearson’s correlation) between lipid peroxidation and toxicity of barracuda liver was found. Because iron and copper are well-known catalysts of hydroxyl radical production and lipid peroxidation in biological systems, the correlation between the concentrations of these metals in barracuda liver and lipid peroxidation and toxicity was also investigated. Cadmium was significantly correlated (p = 0.014) with the toxicity of barracuda livers. This study provides the first data concerning the concentration of iron, copper, and cadmium in the liver of the Caribbean barracuda. Of the three metals studied in barracuda liver, iron was the most abundant, followed by copper and cadmium. Lipid peroxidation was highly variable and detected in five (36%) of the liver samples. Lipid peroxidation was not statistically significantly correlated (p > 0.05) with concentrations of iron, copper, and cadmium in barracuda liver. Collectively, these findings provide additional evidence that lipid peroxidation can be a mechanistic component of ciguatera toxicity in the Caribbean barracuda.     

Frequency of cyanogenesis in tropical rainforests of far north Queensland, Australia

BACKGROUND AND AIMS: Plant cyanogenesis is the release of toxic cyanide from endogenous cyanide-containing compounds, typically cyanogenic glycosides. Despite a large body of phytochemical, taxonomic and ecological work on cyanogenic species, little is known of their frequency in natural plant communities. This study aimed to investigate the frequency of cyanogenesis in Australian tropical rainforests. Secondary aims were to quantify the cyanogenic glycoside content of tissues, to investigate intra-plant and intra-population variation in cyanogenic glycoside concentration and to appraise the potential chemotaxonomic significance of any findings in relation to the distribution of cyanogenesis in related taxa. METHODS: All species in six 200 m(2) plots at each of five sites across lowland, upland and highland tropical rainforest were screened for cyanogenesis using Feigl-Anger indicator papers. The concentrations of cyanogenic glycosides were accurately determined for all cyanogenic individuals. KEY RESULTS: Over 400 species from 87 plant families were screened. Overall, 18 species (4.5 %) were cyanogenic, accounting for 7.3 % of total stem basal area. Cyanogenesis has not previously been reported for 17 of the 18 species, 13 of which are endemic to Australia. Several species belong to plant families or orders in which cyanogenesis has been little reported, if at all (e.g. Elaeocarpaceae, Myrsinaceae, Araliaceae and Lamiaceae). A number of species contained concentrations of cyanogenic glycosides among the highest ever reported for mature leaves-up to 5.2 mg CN g(-1) d. wt, for example, in leaves of Elaeocarpus sericopetalus. There was significant variation in cyanogenic glycoside concentration within individuals; young leaves and reproductive tissues typically had higher cyanogen content. In addition, there was substantial variation in cyanogenic glycoside content within populations of single species. CONCLUSIONS: This study expands the limited knowledge of the frequency of cyanogenesis in natural plant communities, includes novel reports of cyanogenesis among a range of taxa and characterizes patterns in intra-plant and intra-population variation of cyanogensis.     

Effect of pH and nitrogen source on aluminium tolerance of rye (Secale cereale L.) and yellow lupin (Lupinus luteus L.)

Soluble aluminium (Al) is a major factor limiting plant growth in acid mineral soils. Aluminium concentrations in soil solutions are mainly determined by soil pH. However, pH also affects the ratio between activities of protons and cationic Al species and the equilibrium between mono-and polynuclear hydroxy-Al species. The phytotoxicity of these species is not yet clear. The objective of the present study was to clarify the role of minor changes of pH in the rhizosphere on Al phytotoxicity in two Al-tolerant plant species by direct control of the pH in the nutrient solution (4.1, 4.3, 4.5) and in addition by varying the pH in the root apoplast using either nitrate or ammonium as N source. The plants were grown in solution culture at constant external pH. Whereas the Al-sensitive plant species barley and horse bean were damaged at very low Al supplies (1.85 μM and 9.3 μM respectively), 222 μM had to be applied to rye and yellw lupin for a comparable inhibition of root elongation. Yellow lupin was initially severely inhibited in root growth by Al, but then gradually recovered from this ‘Al shock’ within 3 days. In contrast to lupin, rye was hardly affected by Al initially, and it took about 16 h until maximum inhibition of root elongation. In the presence of nitrate, raising the pH from 4.1 to 4.5 aggravated root-growth depression by Al in rye and lupin. Whereas rye roots were severely damaged by ammonium especially at low pH, lupin was rather indifferent to the N source. Aluminium toxicity was less severe in presence of ammonium compared to nitrate N. This effect was less clear with rye at lower pH, because of it's higher proton sensitivity compared to lupin. Less Al injury at lower pH and in presence of ammonium was related to lower Al concentrations in the 1 cm root tips. The results are compatible with data showing high phytotoxicity of mononuclear and polynuclear hydroxy-Al species. However, they could also be interpreted in the light of proton amelioration of Al toxicity owing to competition for Al-sensitive binding sites in the root apoplast.     

Toxicity of the entomopathogenic bacteria Photorhabdus and Xenorhabdus to the mushroom mite (Luciaphorus sp.; Acari: Pygmephoridae)

The mushroom mite, Luciaphorus sp. is a serious pest of tropical mushrooms. We determined the pathogenicity and toxicity of species and strains of the entomopathogenic bacteria, Photorhabdus and Xenorhabdus to the mite. As these bacteria are known to produce antifungal substances, we first determined the effect of 21 species and strains of the bacteria on the mycelial growth of the mushroom, Lentinus squarrosulus. We then determined the toxicity of the eight species and strains of bacteria that did not show any effect on mushroom growth against both the female and male mites. All eight species and strains of the bacteria were toxic to the female mite resulting in significant mite mortality within 24-48 h. Cell-free supernatants from all the eight bacterial species and strains were also toxic to the female mite inflicting significant mortality within 24-48 h. The supernatants of two strains, GPS12 and GPS11, of Photorhabdus luminescens ssp. laumondii were significantly more toxic than the other species and strains to the female mite, resulting in 90-95% mite mortality within 48 h. Both the concentration and age of the bacteria had significant effect on the toxicity of the supernatants to the female mite. None of the bacteria showed toxicity to the male mite which has undeveloped mouthparts. These results indicate that P. luminescens ssp. laumondii and its byproducts are directly toxic to the female mite, suggesting the potential of developing a novel biological approach for the control of this mushroom pest. This is the first report on the miticidal activity of the entomopathogenic bacteria, Photorhabdus and Xenorhabdus.