不同浓度Fe2+与Zn2+对羊草幼苗生长和生理特性的影响

以羊草幼苗为研究对象,通过调整全营养培养基(CK,0.05 mmol/L Fe²⁺、0.015 mmol/L Zn²⁺)中铁或者锌含量设置0、10倍、20倍Fe²⁺(Zn²⁺)浓度处理Fe₀(Zn₀)、Fe₁₀(Zn₁₀)、Fe₂₀(Zn₂₀),以及在高铁培养基中单独添加0.15 mmol/L Zn²⁺或同时添加10 mmol/L Ca²⁺、5 mmol/L Mg²⁺、20 mmol/L K⁺处理,测定培养6 d后幼苗生长指标和矿质元素含量、以及高铁(Fe₂₀)处理下幼苗根中抗氧化指标和相关基因表达量,探究不同浓度Fe²⁺、Zn²⁺对羊草幼苗生长、矿质元素吸收积累及抗氧化指标、基因表达的影响。结果表明：(1)缺锌(Zn₀)显著抑制羊草幼苗鲜重的增加和Zn元素的积累,但促进Fe、Mg元素的积累;高浓度锌(Zn₁₀、Zn₂₀)显著促进幼苗叶片生长和Zn元素的积累;缺铁(Fe₀)显著抑制幼苗的根长、鲜重和Fe元素的积累,促进Mg、Zn元素的积累;高浓度铁(Fe₁₀、Fe₂₀)显著抑制羊草幼苗根叶生长、根毛发育和Ca、Zn、Mg、K元素的积累。(2)增加Zn²⁺和Ca²⁺、Mg²⁺、K⁺浓度无法恢复高铁胁迫对幼苗生长的抑制作用。(3)高浓度铁(Fe₂₀)处理羊草幼苗48 h后,根部过氧化物酶、超氧化物歧化酶、过氧化氢酶、抗坏血酸过氧化物酶、谷胱甘肽还原酶活性和丙二醛、抗坏血酸、还原型谷胱甘肽含量显著升高;烟酰胺合成酶基因、过氧化物酶基因表达量显著下调,植物类萌发素蛋白基因表达量显著上调。研究发现,羊草幼苗生长发育和矿质元素积累对环境中Zn²⁺浓度变化不敏感,却受到环境中高浓度Fe²⁺的显著抑制,并造成严重的氧化胁迫伤害,这种伤害无法在添加Zn²⁺或同时添加Ca²⁺、Mg²⁺、K⁺的条件下恢复。     

The spatial distribution of cations in nematocytes of Hydra vulgaris

The spatial distribution of cations was assayed qualitatively and quantitatively in tentacular nematocytes of Hydra vulgaris in a scanning transmission electron microscope by means of x-ray microanalysis performed on 100 nm thick freeze-dried cryosections. The matrix of undischarged cysts (stenoteles, desmonemes and isorhizas) was found to contain mainly K⁺. In isolated nematocysts of Hydra the intracapsular potassium can be readily substituted by practically any other mono- and divalent cation (Na⁺, NH₄ ⁺, Mn²⁺, Co²⁺, Mg²⁺, Ca²⁺, Fe²⁺) all, except Fe²⁺, without impairing the ability of the cyst to respond to the chemical triggering with dithioerythritol or proteases. Monovalent cations increase the osmotically generated intracapsular pressure compared to divalent ions.     

Inhibition of the biosynthesis ofN-acetylneuraminic acid by metal ions and seleniumin vitro

In liver homogenate the biosynthesis ofN-acetylneuraminic acid usingN-acetylglucosamine as precursor can be followed stepwise by applying different chromatographic procedures. In this cell-free system 16 metal ions (Zn²⁺, Mn²⁺, La³⁺, Co²⁺, Cu²⁺, Hg²⁺, VO ₃ ^– , Pb²⁺, Ce³⁺, Cd²⁺, Fe²⁺, Fe³⁺, Al³⁺, Sn²⁺, Cs⁺ and Li⁺) and the selenium compounds, selenium(IV) oxide and sodium selenite, have been checked with respect to their ability to influence a single or possible several steps of the biosynthesis ofN-acetylneuraminic acid. It could be shown that the following enzymes are sensitive to these metal ions (usually applied at a concentration of 1 mmoll^–1):N-acetylglucosamine kinase (inhibited by Zn²⁺ and vandate), UDP-N-acetylglucosamine-2-epimerase (inhibited by zn²⁺, Co²⁺, Cu²⁺, Hg²⁺, VO ₃ ^– , Pb²⁺, Cd²⁺, Fe³⁺, Cs⁺, Li⁺, selenium(IV) oxide and selenite), andN-acetylmannosamine kinase (inhibited by Zn²⁺, Cu²⁺, Cd²⁺, and Co²⁺). Dose dependent measurements have shown that Zn²⁺, Cu²⁺ and selenite are more efficient inhibitors of UDP-N-acetylglucosamine-2-epimerase than vanadate. As for theN-acetylmannosamine kinase inhibition, a decreasing inhibitory effect exists in the following order Zn²⁺, Cd²⁺, Co²⁺ and Cu²⁺. In contrast, La³⁺, Al³⁺ and Mn²⁺ (1 mmoll^–1) did not interfere with the biosynthesis ofN-acetylneuraminic acid. Thus, the conclusion that the inhibitory effect of the metal ions investigated cannot be regarded as simply unspecific is justified.Dedicated to Professor Theodor Günther on the occasion of his 60th birthday     

Purification and Characterization of Killer Toxin from a Marine Yeast <Emphasis Type="Italic">Pichia anomala</Emphasis> YF07b Against the Pathogenic Yeast in Crab

The molecular mass of the purified killer toxin from the marine killer yeast YF07b was estimated to be 47.0 kDa. The optimal pH and temperature of the purified killer toxin were 4.5 and 40°C, respectively. The toxin was activated by Ca²⁺, K⁺, Na⁺, Mg²⁺, Na⁺, and Co²⁺. However, Fe²⁺, Fe³⁺, Hg²⁺, Cu²⁺, Mn²⁺, Zn²⁺, and Ag⁺ acted as inhibitors in decreasing activity of the toxin. The toxin was strongly inhibited by phenylmethanesulphonyl fluoride (PMSF), iodoacetic acid, ethylenediaminetetraacetic acid, and 1,10-phenanthroline. The Km of the toxin for laminarin was 1.17 g L⁻¹. The toxin also actively hydrolyzed laminarin and killed the whole cells of the pathogenic yeast in crab.     

Effect of prooxidants on yeast mitochondria

Tightly coupled mitochondria from Yarrowia lipolytica and Dipodascus (Endomyces) magnusii yeasts were used in this study. The two yeasts are aerobes containing the fully competent respiratory chain with three energy conservation sites. Interaction of the yeast mitochondria with prooxidants (diamide, menadione, oxaloacetate, phenylarsine oxide, hydrogen peroxide, t-butyl peroxide, and ascorbate plus Fe²⁺) was studied. The prooxidants, depending on their chemical nature, either caused uncoupling (e.g., activated state 4 respiration) or inhibited oxidation of respiratory substrates. All of the agents dissipated the membrane potential without megachannel formation (no large-scale swelling of mitochondria was observed). Except for combined application of ascorbate and Fe²⁺, the prooxidant-induced decrease in the membrane potential was specifically prevented by ATP, even in the cases when classic antioxidants, e.g., N-acetylcysteine, were ineffective. No permeabilization of yeast mitochondria was observed under concerted action of prooxidants and Ca²⁺, suggesting that an mPTP-like pore, if it ever occurs in yeast mitochondria, is not coupled with Ca²⁺ uptake.     

Purification and characterization of two cold-adapted extracellular tannin acyl hydrolases from an Antarctic strain <Emphasis Type="Italic">Verticillium</Emphasis> sp. P9

Two extracellular tannin acyl hydrolases (TAH I and TAH II) produced by an Antarctic filamentous fungus Verticillium sp. P9 were purified to homogeneity (7.9- and 10.5-fold with a yield of 1.6 and 0.9%, respectively) and characterized. TAH I and TAH II are multimeric (each consisting of approximately 40 and 46 kDa sub-units) glycoproteins containing 11 and 26% carbohydrates, respectively, and their molecular mass is approximately 155 kDa. TAH I and TAH II are optimally active at pH of 5.5 and 25 and 20°C, respectively. Both the enzymes were activated by Mg²⁺and Br⁻ ions and 0.5–2.0 M urea and inhibited by other metal ions (Zn²⁺, Cu²⁺, K⁺, Cd²⁺, Ag⁺, Fe³⁺, Mn²⁺, Co²⁺, Hg²⁺, Pb²⁺ and Sn²⁺), anions, Tween 20, Tween 60, Tween 80, Triton X-100, sodium dodecyl sulphate, β-mercaptoethanol, α-glutathione and 4-chloromercuribenzoate. Both tannases more efficiently hydrolyzed tannic acid than methyl gallate. E _a of these reactions and temperature dependence (at 0–30°C) of k _cat, k _cat/K _m, ΔG*, ΔH* and ΔS* for both the enzymes and substrates were determined. The k _cat and k _cat/K _m values (for both the substrates) were considerably higher for the combined preparation of TAH I and TAH II.     

Characterization of K+ Channels in the Basolateral Membrane of Rat Tracheal Epithelia

To study K⁺ channels in the basolateral membrane of chloride-secreting epithelia, rat tracheal epithelial monolayers were cultured on permeable filters and mounted into an Ussing chamber system. The mucosal membrane was permeabilized with nystatin (180 μg/ml) in the symmetrical high K⁺ (145 mm) Ringer solution. During measurement of the macroscopic K⁺ conductance properties of the basolateral membrane under a transepithelial voltage clamp, we detected at least two types of K⁺ currents: one is an inwardly rectifying K⁺ current and the other is a slowly activating outwardly rectifying K⁺ current. The inwardly rectifying K⁺ current is inhibited by Ba²⁺. The slowly activating K⁺ current was potentiated by cAMP and inhibited by clofilium, phorbol 12-myristae 13-acetate (PMA) and lowering temperature. This is consistent with the biophysical characteristics of I _SK channel. RT-PCR analysis revealed the presence of I _SK cDNA in the rat trachea epithelia. Although 0.1 mm Ba²⁺ only had minimal affect on short-circuit current (I _sc) induced by cAMP in intact epithelia, 0.1 mm clofilium strongly inhibited it. These results indicate that I _SK might be important for maintaining cAMP-induced chloride secretion in the rat trachea epithelia. Received: 1 March 1996/Revised: 5 August 1996     

Mechanisms of Saccharomyces Cerevisiae PMA1 H+-ATPase inactivation by Fe2+, H2O2 and Fenton reagents

Although considerably more oxidation-resistant than other P-type ATPases, the yeast PMA1 H⁺-ATPase of Saccharomyces cerevisiae SY4 secretory vesicles was inactivated by H₂O₂, Fe²⁺, Fe- and Cu-Fenton reagents. Inactivation by Fe²⁺ required the presence of oxygen and hence involved auto-oxidation of Fe²⁺ to Fe³⁺. The highest Fe^2- (100 μM) and H₂O₂ (100 mM) concentrations used produced about the same effect. Inactivation by the Fenton reagent depended more on Fe²⁺ content than on H₂O₂ concentration, occurred only when Fe²⁺ was added to the vesicles first and was only slightly reduced by scavengers (mannitol, Tris, NaN₃, DMSO) and by chelators (EDTA, EGTA, DTPA, BPDs, bipyridine, 1, 10-phenanthroline). Inactivation by Fe- and Cu- Fenton reagent was the same; the identical inactivation pattern found for both reagents under anaerobic conditions showed that both reagents act via OH^·. The lipid peroxidation blocker BHT prevented Fenton-induced rise in lipid peroxidation in both whole cells and in isolated membrane lipids but did not protect the H⁺-ATPase in secretory vesicles against inactivation. ATP partially protected the enzyme against peroxide and the Fenton reagent in a way resembling the protection it afforded against SH-specific agents. The results indicate that Fe²⁺ and the Fenton reagent act via metal-catalyzed oxidation at specific metal-binding sites, very probably SH-containing amino acid residues. Deferrioxamine, which prevents the redox cycling of Fe²⁺, blocked H⁺-ATPase inactivation by Fe²⁺ and the Fenton reagent but not that caused by H₂O₂, which therefore seems to involve a direct non-radical attack. Fe-Fenton reagent caused fragmentation of the H⁺-ATPase molecule, which, in Western blots, did not give rise to defined fragments bands but merely to smears.     

Dried field populations of Nostoc flagelliforme (Cyanophyceae) require exogenous nutrients for their photosynthetic recovery

The effects of nutrients on the photosynthetic recovery of Nostoc flagelliforme during re-hydration were investigated in order to see if their addition was necessary. Net photosynthesis was negligible in distilled water without nutrient-enrichment. Addition of K⁺ resulted in significant enhancement of net photosynthesis, whereas other nutrients (Fe³⁺, Mg²⁺, Na⁺, NO₃ ^-, PO₄ ^3-, Cl^-) and trace-metals (A₅) showed little effect. The recovered net photosynthetic activity increased with the increased K⁺, and reached the maximum at concentrations above 230 μM. Desiccation and re-hydration did not affect the dependence of photosynthetic recovery on K⁺. It was concluded that dried field populations of N. flagelliforme require exogenous addition of potassium for photosynthetic recovery and that growth may be potassium-limited in nature. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of the growth and solubilization capabilities of <Emphasis Type="Italic">Trichoderma harzianum</Emphasis> T1

The growth capability of Trichoderma harzianum Rifaii Tl was tested on Malt Extract and Czapeks Dox agar containing different concentrations of Cu²⁺, Zn²⁺, Mn²⁺, Fe²⁺ and Ca²⁺. The T. harzianum Tl isolate was observed to produce mycelia and spores in various mineral-containing media. It showed the lowest tolerance to Ca²⁺ and the highest tolerance to Fe²⁺. Solubilization capability of T. harzianum Tl for some insoluble minerals via acidification of medium has been tested on MnO₂, CuO, Fe₂O₃ and metallic Zn. T. harzianum Tl was able to solubilize MnO₂ and metallic Zn in a liquid medium.     

Reversible sporicidal action of cuprous ions

At 10 mM, Cu⁺ was highly protective against killing of spores of Bacillus megaterium ATCC 19213 by H₂O₂, while at higher concentrations, from 15–100 mM, killing was augmented. In contrast, Cu²⁺, Fe²⁺, Fe³⁺, Co²⁺ or Co³⁺ ions acted only protectively. Cu⁺ itself was sporicidal in the absence of H₂O₂ or ascorbate, and its sporicidal action did not depend on generation of highly reactive oxygen species. It appeared that killing involved either inhibition of germination or copper toxicity to germinated cells in that Cu⁺-inactivated spores did not germinate readily but chemical decoating of the cells prior to plating on a solid medium resulted in reversal of the sporicidal effect. Received 12 July 1996/ Accepted in revised form 03 November 1996     

“Chelatable iron pool”: inositol 1,2,3-trisphosphate fulfils the conditions required to be a safe cellular iron ligand

Mammalian cells contain a pool of iron that is not strongly bound to proteins, which can be detected with fluorescent chelating probes. The cellular ligands of this biologically important “chelatable”, “labile” or “transit” iron are not known. Proposed ligands are problematic, because they are saturated by magnesium under cellular conditions and/or because they are not “safe”, i.e. they allow iron to catalyse hydroxyl radical formation. Among small cellular molecules, certain inositol phosphates (InsPs) excel at complexing Fe³⁺ in such a “safe” manner in vitro. However, we previously calculated that the most abundant InsP, inositol hexakisphosphate, cannot interact with Fe³⁺ in the presence of cellular concentrations of Mg²⁺. In this work, we study the metal complexation behaviour of inositol 1,2,3-trisphosphate [Ins(1,2,3)P ₃], a cellular constituent of unknown function and the simplest InsP to display high-affinity, “safe”, iron complexation. We report thermodynamic constants for the interaction of Ins(1,2,3)P ₃ with Na⁺, K⁺, Mg²⁺, Ca²⁺, Cu²⁺, Fe²⁺ and Fe³⁺. Our calculations indicate that Ins(1,2,3)P ₃ can be expected to complex all available Fe³⁺ in a quantitative, 1:1 reaction, both in cytosol/nucleus and in acidic compartments, in which an important labile iron subpool is thought to exist. In addition, we calculate that the fluorescent iron probe calcein would strip Fe³⁺ from Ins(1,2,3)P ₃ under cellular conditions, and hence labile iron detected using this probe may include iron bound to Ins(1,2,3)P ₃. Therefore Ins(1,2,3)P ₃ is the first viable proposal for a transit iron ligand. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Improved expression of a soluble single chain antibody fusion protein containing tumor necrosis factor in <Emphasis Type="Italic">Escherichia coli</Emphasis>

An epoxide hydrolase gene of about 0.8 kb was cloned from Rhodococcus opacus ML-0004, and the open reading frame (ORF) sequence predicted a protein of 253 amino acids with a molecular mass of about 28 kDa. An expression plasmid carrying the gene under the control of the tac promotor was introduced into Escherichia coli, and the epoxide hydrolase gene was successfully expressed in the recombinant strains. Some characteristics of purified recombinant epoxide hydrolase were also studied. Epoxide hydrolase showed a high stereospecificity for l(+)-tartaric acid, but not for d(+)-tartaric acid. The epoxide hydrolase activity could be assayed at the pH ranging from 3.5 to 10.0, and its maximum activity was obtained between pH 7.0 and 7.5. The enzyme was sensitive to heat, decreasing slowly between 30°C and 40°C, and significantly at 45°C. The enzyme activity was activated by Ca²⁺ and Fe²⁺, while strongly inhibited by Ag⁺ and Hg⁺, and slightly inhibited by Cu²⁺, Zn²⁺, Ba²⁺, Ni⁺, EDTA–Na₂ and fumarate.     

Purification of glucose‐6‐phosphate dehydrogenase from rat (Rattus norvegicus) erythrocytes and inhibition effects of some metal ions on enzyme activity

Glucose‐6‐phosphate dehydrogenase (G6PD) is the first enzyme on which the pentose phosphate pathway was checked. In this study, purification of a G6PD enzyme was carried out by using rat erythrocytes with a specific activity of 13.7 EU/mg and a yield of 67.7 and 155.6‐fold by using 2′,5′‐ADP Sepharose‐4B affinity column chromatography. For the purpose of identifying the purity of enzyme and molecular mass of the subunit, a sodium dodecyl sulfate‐polyacrylamide gel electrophoresis was carried out. The molecular mass of subunit was calculated 56.5 kDa approximately. Then, an investigation was carried out regarding the inhibitory effects caused by various metal ions (Fe²⁺, Pb²⁺, Cd²⁺, Ag⁺, and Zn²⁺) on G6PD enzyme activities, as per Beutler method at 340 nm under in vitro conditions. Lineweaver–Burk diagrams were used for estimation of the IC₅₀ and K_i values for the metals. K_i values for Pb⁺², Cd⁺², Ag⁺, and Zn⁺² were 113.3, 215.2, 19.4, and 474.7 μM, respectively.     

Bacterial Pu(V) reduction in the absence and presence of Fe(III)–NTA: modeling and experimental approach

Plutonium (Pu), a key contaminant at sites associated with the manufacture of nuclear weapons and with nuclear-energy wastes, can be precipitated to “immobilized” plutonium phases in systems that promote bioreduction. Ferric iron (Fe³⁺) is often present in contaminated sites, and its bioreduction to ferrous iron (Fe²⁺) may be involved in the reduction of Pu to forms that precipitate. Alternately, Pu can be reduced directly by the bacteria. Besides Fe, contaminated sites often contain strong complexing ligands, such as nitrilotriacetic acid (NTA). We used biogeochemical modeling to interpret the experimental fate of Pu in the absence and presence of ferric iron (Fe³⁺) and NTA under anaerobic conditions. In all cases, Shewanella alga BrY (S. alga) reduced Pu(V)(PuO₂ ⁺) to Pu(III), and experimental evidence indicates that Pu(III) precipitated as PuPO_4(am). In the absence of Fe³⁺ and NTA, reduction of PuO₂ ⁺ was directly biotic, but modeling simulations support that PuO₂ ⁺ reduction in the presence of Fe³⁺ and NTA was due to an abiotic stepwise reduction of PuO₂ ⁺ to Pu⁴⁺, followed by reduction of Pu⁴⁺ to Pu³⁺, both through biogenically produced Fe²⁺. This means that PuO₂ ⁺ reduction was slowed by first having Fe³⁺ reduced to Fe²⁺. Modeling results also show that the degree of PuPO_4(am) precipitation depends on the NTA concentration. While precipitation out-competes complexation when NTA is present at the same or lower concentration than Pu, excess NTA can prevent precipitation of PuPO_4(am).     

黑河天涝池流域典型林分生态水文化学特征

采集了黑河天涝池流域典型林分林外雨、穿透雨、树干径流和枯透水,并检测水体pH值和12种离子(K~+、Ca~(2+)、Na~+、Mg~(2+)、NH_4~+、Cu~(2+)、Zn~(2+)、Pb~(2+)、Cd~(2+)、Cl~-、SO_4~(2-)、NO_3~3)的质量浓度。结果表明:天涝池流域大气降水pH均值为7.74,呈碱性,降水中离子绝对质量浓度较低,最高的是NO_3~-,质量浓度为1.1111 mg/L,最低的为Na~+,质量浓度为0.0108 mg/L;两种林分冠层有降低降雨pH值的作用,青海云杉林冠层对NH_4~+有升高作用,祁连圆柏林冠层对NH_4~+有降低作用,两种林冠层对NO_3~-和Cu~(2+)质量浓度有降低作用,对其它离子质量浓度均表现为升高作用;两种林分树干径流有提高穿透雨pH值的作用,与穿透雨相比,两种林分树干径流中阴离子均有升高,圆柏树干径流中所有阳离子质量浓度均有下降,云杉树干径流中Ca~(2+)、K~+、Mg~(2+)和Na~+减少,NH_4~+和Cu~(2+)增加;典型林分枯透水有提升穿透雨pH值的作用,与穿透雨相比,两种林分枯透水中阴离子质量浓度均有升高,云杉枯透水各阳离子均有降低,圆柏枯透水中Ca~(2+)、K~+和Mg~(2+)质量浓度升高,NH_4~+、Na~+和Cu~(2+)质量浓度下降;在采集的所有样本中,Pb~(2+)和Cd~(2+)均未检出,而Zn~(2+)仅在云杉树干径流中检出。     

Purification and characterization of extracellular inulinase from a marine yeast <Emphasis Type="Italic">Pichia guilliermondii</Emphasis> and inulin hydrolysis by the purified inulinase

The extracellular inulinase of the marine yeast Pichia guilliermondii strain 1 was purified to homogeneity resulting in a 7.2-fold increase in specific inulinase activity. The molecular mass of the purified enzyme was estimated to be 50.0 kDa. The optimal pH and temperature for the purified enzyme were 6.0 and 60°C, respectively. The enzyme was activated by Mn²⁺, Ca²⁺, K⁺, Li⁺, Na⁺, Fe³⁺, Fe²⁺, Cu²⁺, and Co²⁺, but Mg²⁺, Hg²⁺, and Ag⁺ inhibited activity. The enzyme was strongly inhibited by phenylmethanesulphonyl fluoride (PMSF), iodoacetic acid, EDTA, and 1, 10-phenanthroline. The K _m and V _max values of the purified inulinase for inulin were 21.1 mg/mL and 0.08 mg/min, respectively. A large number of monosaccharides were detected after the hydrolysis of inulin. The deduced protein sequence from the cloned P. guilliermondii strain 1 inulinase gene contained the consensus motifs R-D-P-K-V-F-W-H and W-M-N-D-P-N-G, which are conserved among the inulinases from other microorganisms.     

Correlations between projection area of ectomycorrhizae and H<Subscript>2</Subscript>O extractable nutrients in organic soil layers

Most of the fine root tips of boreal and temperate forests are colonized by ectomycorrhizal fungi. Thus ectomycorrhizal (ECM) symbiosis is an important factor in supplying trees with water and a wide range of nutrients. ECM are frequently patchily distributed and often form dense systems in small areas. One of the reasons for this uneven distribution might be a heterogeneous and patchy distribution of nutrients. The present study compares the occurrence of ECM of Cortinarius obtusus, Lactarius decipiens, L. theiogalus, and Russula ochroleuca and soil nutrient concentrations at a micro-scale (1 cm²) in the O_F layer of a pure Norway spruce stand. In addition to the macronutrients K⁺, Mg²⁺, Ca²⁺, NO₃ ⁻, NH₄ ⁺, the concentrations of Na⁺, Fe³⁺+Mn²⁺, Al³⁺, Cl⁻, SO₄ ²⁻ are studied, as well as pH. Whereas Russula ochroleuca and Lactarius decipiens did not reveal any significant correlation with any of the tested nutrients or pH, the occurrence of L. theiogalus was significantly (p < 5 %) positively correlated with NH₄ ⁺, K⁺, Na⁺, Mg²⁺, Fe³⁺+Mn²⁺, and pH. Cortinarius obtusus was positively correlated at the same significance level only with NH₄ ⁺ and Mg²⁺.     

Protective effects of pretreatment with Fe2+, Cu2+, and Rb+ on phoxim poisoning in silkworm,Bombyx mori

BackgroundPhoxim is a widely used organophosphorus pesticide in agriculture. People are paying more and more attention to its toxicity. At present, there is no appropriate way to solve the phoxim poisoning of silkworm, which severely affected the development of sericulture. Fe²⁺, Cu²⁺, Rb⁺ exerted their biological effects through various forms in vivo.MethodsTo evaluate the effect of Fe²⁺/Cu²⁺/Rb⁺ on phoxim poisoning in silkworm, Bombyx mori were treated with fresh mulberry leaves soaked in 2.5 mg/L phoxim for 2 min with 50 mg/L FeCl₂, 150 mg/L CuCl₂, or 0.5 mg/L RbCl from 5 days of the fifth-instar silkworm.ResultsFe²⁺, Cu²⁺, and Rb⁺ pretreatments significantly inhibited the phoxim-induced reduction of survival rate and alleviated the phoxim-induced poisoning symptoms. The protective effects of Fe²⁺, Cu²⁺, and Rb⁺ on phoxim poisoning might be due to their enhancement of superoxide dismutase (SOD), catalase (CAT), and carboxylesterase (CarE) in the hemolymph and fat body of silkworm. This enhancement might reduce reactive oxygen species (ROS) accumulation and oxidative stress (OS) caused by phoxim poisoning. Thereby it reduced the damage to silkworm tissues and cells.ConclusionsThese results showed that Fe²⁺, Cu²⁺, and Rb⁺ treatments protected the silkworm from phoxim poisoning by directly enhancing the activity of SOD, CAT, and CarE enzymes and reducing oxidative stress, but not dependent on the high expression of CYP genes. The use of Fe²⁺, Cu²⁺, and Rb⁺ to enhance the activity of SOD, CAT, and CarE enzymes may be an underlying effective way to solve phoxim poisoning in the silkworm industry.     

Fluorescent labeling of (Na + K)-ATPase by 5-iodoacetamidofluorescein

5-Iodoacetamidofluorescein (5-IAF) covalently labels dog kidney (Na⁺ + K⁺)-ATPase with approximately 2 moles incorporated per mole of enzyme. ATPase and K⁺-phosphatase activities are fully retained after reaction, and the kinetic parameters for Na⁺, K⁺, Mg²⁺, ATP and p-nitrophenyl phosphate are likewise not significantly affected. The fluorescence of the bound 5-IAF is increased by ATP, Na⁺, and Mg²⁺, and decreased by K⁺. These fluorescence changes likely reflect ligand-induced stabilization of the E₁ or E₂ states of the enzyme.