The protective effect of selenium inorganic forms against cadmium and silver toxicity in mycelia of Pleurotus ostreatus

The effect of two inorganic selenium forms has been investigated in the mycelia of Pleurotus ostreatus exposed to cadmium and silver salts in the shaken cultures. The degree of toxicity was assessed by the determination of malondialdehyde (MDA; a common biomarker of lipid peroxidation). The mycelia were exposed to one element form (up to 5 mg l⁻¹) and also to the following combinations: cadmium(II) + selenium(IV); cadmium(II) + selenium(VI); silver(I) + selenium(IV); silver(I) + selenium(VI). The concentrations of cadmium, silver, selenium, and MDA were assessed in the mixed cytosol and cell membrane fractions (CCM). A positive correlation between MDA and cadmium was found in the CCM (β = 0.7775, P = 0.0001), whereas the effect of silver was less significant (β = 0.4642, P = 0.039). These results indicate that silver(I) and cadmium(II) have different capacities to induce lipid peroxidation in P. ostreatus. The protective role of selenium against metal-induced oxidative damage was found to be dependent on the oxidation state of the element form in the growth medium. The strongest beneficial effect was observed in mycelia exposed to cadmium(II) + selenium(IV) (inverse correlation between MDA and selenium in the CCM: β = −0.7129, P = 0.009) and it has been ascribed to a lower incorporation of the toxic metal and/or to possible intracellular interaction between selenium and cadmium. Under exposure to silver(I), the protective effect of selenium(IV) was less noticeable (correlation between MDA and selenium in the CCM; β = −0.6068, P = 0.036); in the presence of selenium(VI), no beneficial effect was observed.     

Ribonucleoside labeling with Os(VI): a methodological approach to evaluation of RNA methylation by HPLC-ICP-MS

Covalent modifications of nucleobases are thought to play an important role in regulating the functions of DNA and various cellular RNA types. Perhaps the best characterized is DNA methylation on cytosine (methyl tag attached to carbon 5 position) and such modification has also been detected in stable and long-lived RNA molecules. In this work, we propose a novel procedure enabling very sensitive quantification of methylcytidine and other ribonucleosides, based on reversed phase liquid chromatography with inductively coupled plasma mass spectrometry (ICP-MS) detection. The procedure relies on labeling ribose residues with osmium, by formation of a ternary complex between cis-diol ribose groups, hexavalent osmium (K(2)OsO(2)(OH)(4)) and tetramethylethylenediamine (TEMED). The derivatization reaction was carried out with 50?:?1 molar excess of Os to ribonucleoside, pH 4, for 2 h at room temperature. The structures of Os-labeled cytidine and methylcytidine were confirmed by electrospray ionization mass spectrometry. The separation of Os-labeled cytidine (C), uridine (U), 5-methylcytidine (5mC) and guanosine (G) was achieved on C18 column (Gemini, 150 × 3 mm, 5 μm) with isocratic elution (0.05% triethylamine + 6 mmol L(-1) ammonium acetate, pH 4.4: methanol (85?:?15)) and a total flow rate 0.6 mL min(-1). The column effluent was on-line introduced to ICP-MS (a model 7500 ce, Agilent Technologies) for specific detection at (189)Os. Calibration was performed within the concentration range 0-200 nmol L(-1) of each ribonucleoside and the analytical figures of merit were evaluated. For 100 μL injection, the detection limits for C, U, 5mC, G were 24, 38, 21 and 28 pmol L(-1), respectively. While introducing Os(vi)-TEMED to the column, it eluted in the dead volume and the detection limit for osmium was 20 pmol L(-1). The results obtained in this work might be helpful in the analysis of RNA digests, providing quantitative data on the ribonucleoside composition and RNA methylation (measured as the percentage of methylated cytidines with respect to total RNA cytidines).     

The 33 kDa protein of photosystem II is a low-affinity calcium- and lanthanide-binding protein

We have shown that the isolated 33 kDa protein of photosystem II contains one calcium and one lanthanide low-affinity binding site with binding constants (K(D)) on the order of 10(-5) M. Binding of calcium or lanthanides to this site induces conformational changes in the protein that manifest in fluorescence emission spectra of the protein, circular dichroism spectra, and calorimetric thermograms where the phase transitions are shifted to lower temperatures. The role of calcium binding to the 33 kDa protein in the attainment of its native structure and the significance of this interaction for the oxygen evolution process are discussed.     

Kinetics of proliferation,cell differentiation,and IgM secretion in the omental lymphoid organ of B10/Sn mice following intraperitoneal immunization with sheep erythrocytes

At different times after single and repeated intraperitoneal injections of SRBC into B10/Sn mice, the [³H]thymidine uptake of omental lymphoid organ (OLO) cells was examined by means of scintillation counting and autoradiographic methods. The specific immune response was assayed by the PFC technique. The first SRBC injection induced, in OLO, proliferative changes in reticulum cells and an intense infiltration with lymphocytes; however, the production of humoral anti-SRBC antibodies was absent. The second immunization provoked the proliferation of lymphoblasts, the appearance of plasmocytes, and the production of specific antibodies of the IgM class only. The results indicate that OLO, thanks to the particular ability of its reticulum cells, presents a microenvironment selectively trapping B lymphocytes and limiting their functional differentiation.     

Determination of total aluminum, chromium, copper, iron, manganese, and nickel and their fractions leached to the infusions of black tea, green tea, Hibiscus sabdariffa, and Ilex paraguariensis (mate) by ETA-AAS

Total aluminum, chromium, copper, iron, manganese, and nickel were determined in black tea, green tea, Hibiscus sabdariffa, and Ilex paraguariensis (mate) by electrothermal atomic absorption spectrometry after nitric/perchloric acid digestion. In each case, one ground sample of commercially available leafy material was prepared and three 0.5-g subsamples were run in parallel. The infusions were also analyzed and the percentage of each element leached into the liquor was evaluated. The obtained results indicated that hibiscus and mate contained lower levels of aluminum (272±19 μg/g and 369±22 μg/g, respectively) as referred to black tea (759±31 μg/g) or green tea (919±29 μg/g) and suggested that mate drinking could be a good dietary source of essential micronutrient manganese (total content 2223±110 μg/g, 48.1% leached to the infusion). It was also found that the infusion of hibiscus could supply greater amounts of iron (111±5 μg/g total, 40.5% leached) and copper (5.9±0.3 μg/g total, 93.4% leached) as compared to other infusions. Moreover, it was found that the percentage of element leached to the infusion was strongly related to the tannins content in the beverage (correlation coefficients >0.82 with the exception for nickel); for lower tannins level, better leaching was observed.     

Inheritance of chorionic malformations and insecticide resistance by Spodoptera exigua

Abstract:  Effect of exposure to the organophosphorus insecticide – fenitrothion [O,O-dimethyl-O-(4-nitro-3-methyl)phenyl] – on four generations of Spodoptera exigua Hübner (Lep., Noctuidae) larvae, with regard to the mortality and structure of the chorion of eggs laid was tested. Generations varied in the total mortality rate, although all of them showed some survival rate. The third and the fourth generations showed the lowest mortality among tested ones. Exposure to fenitrothion caused malformations in eggs. The chorion revealed cracks and diminutions of the outer layer. The quality and quantity of malformations increased proportional to the duration of exposure, e.g. the second exposed generation reveald more prominent changes than the first one. Malformations were observed in the next generations, which were not exposed to pesticide. The follicular cells, which are responsible for the structure and sculpture of the eggshell, must have inherited the malforming mechanism. Most probably, malformation takes place during the late development of eggs in the ovarioles.     

Characteristics of action potentials in Helianthus annuus

The action potentials induced by nondamaging electrical stimuli in 16- to 22-day-old plants of Helianthus annuus were examined. Typical recordings are presented. Mean values of their amplitudes and conduction velocities in the stem, the strength-duration relation, the 'all-or-none' law and the refractory periods have been determined. The amplitude and velocity of propagation were essentially identical in the upward and downward direction, but greater in the upper than in the lower half. In 'electrically active' plants, the rheobase value is 2 V, the minimum period for stimulation is 1.8 s. and the chronaxie 2.3 s. It is noted that the excitability level between similar plants on the same day and in the same plant on different days is highly variable and undergoes periodic changes.