Generation of superoxide anion and induction of superoxide dismutase and peroxidase in bean leaves infected with pathogenic fungi.

Generation of superoxide anion (O2-.) and peroxidase activity were significantly increased in bean leaves infected with incompatible and compatible pathogens: Botrytis fabae and Botrytis cinerea, respectively, but the induction was greater on direct inoculation with B. fabae, than with B. cinerea. A slightly higher O2-. level was also detected in the parts of leaves surrounding the inoculation side. Overproduction of O2-. was observed earlier than the increase in peroxidase activity. Pretreatment of the leaves with methyl jasmonate enhanced both O2-. production and peroxidase activity following inoculation with B. cinerea. Induction of superoxide dismutase activity after the infection was less pronounced than changes in O2-. level. The differences in the rate of NADH oxidation in the extracts from control and inoculated leaves, correlated with the differences in the rate of O2-. production. The results indicate that O2-. level is one of the essential factors responsible for the difference in the interactions between bean plant and compatible and incompatible pathogens.

Evidence of differential hematopoietic compensation to lead intoxication in blood, liver and kidney.

The dependence of fluorescent porphyrin levels on the concentration of lead in blood, liver and kidney has been examined as functions of both the level and duration of dosing. Individually housed male Wistar COBS rats of 200 g were randomly selected for 3, 7, 21 and 35 day dosing periods in groups of: control, 50, 100 and 1000 ppm dosing in drinking water. The plot of all data points for porphyrin concentration against measured lead burden covers the same range of levels and closely resembles the scatter of data observed in humans. However, subsets of this plot defined by individual dose levels and durations yield well-defined linear relationships. At all dose levels at 7 days the correlation of porphyrin concentration to lead tissue burden is negative in all tissues, showing a direct inhibition of hemopoiesis with lead burden. Depending on the tissue the slope becomes less negative, or, as in blood, positive at 21 and 35 days at all doses. This compensation is most rapid in blood, then liver and is least evident in kidney. The time at which compensation is observed is the same for all doses in each tissue and seems therefore, to depend on the rate of protein turnover in different tissue types. These results suggest that a direct correlation of porphyrin concentration to lead burden is not valid without knowledge of the dosing history. As well, evidence of compensation in one tissue does not imply successful compensation in other affected tissues where regeneration rates are slower.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of the relationship between chemical and biological monitoring of low-level lead poisoning.

Blood lead levels, together with delta-aminolevulinic acid dehydratase activity determinations have been measured on rats dosed with up to 1000 ppm lead acetate in their drinking water for periods up to 5 weeks. Despite evidence of a compensation mechanism developing in the enzyme determinations, enzyme activity ratios, if properly chosen, still correlate reasonably well (r = 0.87) with blood lead levels. Activity ratios using data on the shoulders of pH-activity profiles (e.g. activity ratios of 6.4 and 7.2), however, give much less satisfactory correlations. These data provide a more stringent test of the chemical monitor-biological monitor correlation than has previously been possible.

Influence of some matrix elements on atomization of cobalt in graphite-furnace atomic-absorption spectrometry.

The influence of some chlorine, sulphur and phosphorus compounds on cobalt atomization in a graphite cuvette has been investigated. On the basis of atomization curves and estimated atomization energies the mechanisms of several processes have been proposed. Excess of chlorine is responsible for losses of cobalt as chloride and also for formation of a compound with graphite which causes atomization to occur at a temperature 300 K higher than that in the absence of graphite. In presence of sulphur, the atomization goes through sulphide formation but a reaction with graphite is also suspected. The presence of phosphorus significantly increases the rate of atomization, which enhances the peak height for cobalt. The mechanism probably involves dissociation of phosphate salts.

Effect of halogenated solvents on iron atomization in graphite-furnace atomic-absorption spectroscopy.

When an iron solution in an organic solvent is examined by atomic-absorption spectroscopy, the signal decreases to below that for a comparable aqueous solution. This effect is most pronounced for halogen-containing solvents because of volatility of FeCl(2), and a change in the atomization curve with a shift towards higher temperatures for atomization. When the cuvette is pretreated with halogenated solvent a double peak is observed. The first peak corresponds to that found for aqueous solvents, the second may be correlated with the peak for iron in a halogenated solvent. The peaksplitting effect of such a solvent increases with halogen:hydrogen ratio in the solvent. The halogen penetrates the structure of the graphite cuvette and probably forms strong carbon-haloge. compounds which modify the atomization conditions for iron. When water is introduced hydrogen halide is formed, which removes the excess of halogen from the atomization region.

Experimental parameters of vanadium determination by atomic-absorption spectroscopy with graphite-furnace atomization.

It was found that impregnation of a graphite cuvette (HGA-72) with salts of elements which form stable carbides (Ta, Si Nb, Zr, W, La) decreases the absorbance signal for vanadium. The slope of the atomization curves indicates that formation of vanadium atoms is inhibited, probably by formation of a ternary compound between the impregnating element, vanadium and graphite. On the contrary bigger signals and better repeatability of results may be achieved when the cuvette is coated with pyrolytic graphite and methane is added to the sheath gas. The presence of methane increases the atomization efficiency and compensates for the disadvantageous influence of any air present in the sheath gas.

Titration curves in complexometric titrations with the redox system Fe(III)/Fe(II).

Potentiometric titrations of metal ions with EDTA have been carried out with a platinum or graphite electrode and the Fe(III)/Fe(II) redox system. In the absence of oxygen and for pH < 2 the titration curves may be described by an equation similar to that given previously for titrations with silver and mercury electrodes. Titration curves for bismuth and indium, which are more strongly complexed than iron, are asymmetrical and useful for analytical purposes. When the titrated ions are complexed less strongly than iron(III) ions the kinetics of metal complexation have a pronounced effect. The titration curves of thorium and copper, which react more rapidly than iron, are analytically useful. The curves recorded rapidly after titrant additions have a better end-point break than those which correspond to thermodynamic equilibrium. When a metal, e.g., nickel, is weakly bound by EDTA, and reacts more slowly than iron, a very small end-point break or none at all is observed.