The Effect of Experimental Methyl Mercury Poisoning on the Number of Sulfhydryl (SH) Groups in the Brain,Liver and Muscle of Rat

Fifteen adult male rats, the “experimental” rats, were fed a daily diet which contained methyl mercury hydroxide combined with liver homogenate. The daily dose of methyl mercury in terms of metallic mercury was 1.8 mg per rat. Six similar rats, the “controls”, were fed the same diet without methyl mercury. After the experimental rats had developed symptoms typical of methyl mercury poisoning, which occurred on the 15th day of the experiment, all the test animals were decapitated. The average total dose of methyl mercury producing toxic symptoms was 58,1 ± 6.1 mg Hg per kg body weight. The sulfhydryl groups and the mercury content of the brains, livers and caudal femoral muscles of the animals were determined. The SH determinations were made by amperometric titration and the mercury determinations by neutron activation analysis.The mean number of SH groups in the brains (14.95 ± 1.97 µM/g) and livers (35.89 ± 4.10 µM/g) of the methyl mercury-fed rats was found to be significantly (P < 0.001 and P < 0.01 respectively) lower than the corresponding means of the livers (17.63 ± 1.12 µM/g) and brains (44.75 ± 5.60 µM/g) of the controls. The number of SH groups in the muscles did not differ significantly between the animal groups (0.5 < P < 0.6). The mean mercury content of the brains, livers and muscles was found to be 26.0, 124.6 and 39.1 p.p.m. respectively, corresponding to 0.12, 0.62 and 0.19 µM per g of tissue. The decrease in the number of SH groups in the brains, 2.68 µM/g, and in the livers, 8.86 µM/g, of the methyl mercury-fed rats is thus considered to be due mainly to other effects of methyl mercury than to the direct binding of this compound to the tissue SH groups.     

Comparison of beta,Johnson’s SB,Weibull and truncated Weibull functions for modeling the diameter distribution of forest stands in Catalonia (north-east of Spain)

The purpose of this study was to compare the beta, Johnson SB, Weibull and truncated Weibull functions in describing the diameter distributions of forest stands in Catalonia. The data consisted of permanent sample plots from the Spanish National Forest Inventory in Catalonia. The empirical data represent left-truncated distributions, as the smallest diameter measured in the field was 7.5 cm. A total of 1,242 plots were used to fit the functions and analyze their performance. The distribution functions were fitted to the diameter distributions of the number of stems (DD_N) and stand basal area (DD_G). The performance of the candidate functions was compared by means of their bias and RMSE for different diameter sums measuring the difference between the empirical and fitted distributions. The leftmost part (from 0 to 7.5 cm) of the non-truncated functions was ignored in this analysis. Sensitivity analyses were conducted to check whether the results depended on the number of trees measured in the stand, or the main species of the stand. The truncated Weibull function for the diameter distribution of stand basal area appeared to be in all cases the most accurate and consistent function. Generally, functions describing the distribution of stand basal area performed better than functions that described the distribution of the number of trees. Of the basal area distributions, beta and Johnson’s SB were the second best and nearly equally good with each other. The order of precision of the tested functions was: truncated Weibull for DD_G, truncated Weibull for DD_N, Johnson’s SB for DD_G, beta for DD_G, beta for DD_N and Weibull for DD_G, Weibull for DD_N, and Johnson’s SB for DD_N.     

Dynamics and potentials of carbon sequestration in managed stands and wood products in Finland under changing climatic conditions

Carbon (C) sequestration was studied in managed boreal forest stands and in wood products under current and changing climate in Finland. The C flows were simulated with a gap-type forest model interfaced with a wood product model. Sites in the simulations represented medium fertile southern and northern Finland sites, and stands were pure Scots pine and Norway spruce stands or mixtures of silver and pubescent birch.

Changing climate increased C sequestration clearly in northern Finland, but in southern Finland sequestration even decreased. Temperature is currently the major factor limiting tree growth in northern Finland. In southern Finland, the total average C balance over the 150 year period increased slightly in Scots pine stands and wood products, from 0.78 Mg C ha⁻¹ per year to 0.84 Mg C ha⁻¹ per year, while in birch stands and wood products the increase was larger, from 0.64 Mg C ha⁻¹ per year to 0.92 Mg C ha⁻¹ per year. In Norway spruce stands and wood products, the total average balance decreased substantially, from 0.96 Mg C ha⁻¹ per year to 0.32 Mg C ha⁻¹ per year. In northern Finland, the total average C balance of the 150 year period increased under changing climate, regardless of tree species: in Scots pine stands and wood products from 1.10 Mg C ha⁻¹ per year to 1.42 Mg C ha⁻¹ per year, in Norway spruce stands and wood products from 0.69 Mg C ha⁻¹ per year to 0.99 Mg C ha⁻¹ per year, and in birch stands and wood products from 0.43 Mg C ha⁻¹ per year to 0.60 Mg C ha⁻¹ per year.

C sequestration in unmanaged stands was larger than in managed systems, regardless of climate. However, wood products should be included in C sequestration assessments since 12–55% of the total 45–214 Mg C ha⁻¹ after 150 years' simulation was in products, depending on tree species, climate and location. The largest C flow from managed system back into the atmosphere was from litter, 36–47% of the total flow, from vegetation 22–32%, from soil organic matter 25–30%. Emissions from the production process and burning of discarded products were 1–6% of the total flow, and emissions from landfills less than 1%.     

Episodicity of Sulphate Deposition in Finland

A characteristic of daily acid deposition data, in particular at remote sites, is the occurrence of some extreme peaks above the base level of moderate values. A large proportion of the annual acid deposition is accumulated in a few days: 5 worst days at the Finnish background stations can bring 20–30 % of the annual bulk sulphate load. The aim of this study was to determine whether there is a difference between stations in the number of extreme daily bulk acid depositions. The bulk deposition of sulphate in the 1990's at five Finnish monitoring stations was used as a reference. Days on which the deposition value exceeded the annual median value of the station by a factor of 10 were counted as episode days. The number of episode days in central and northern Finland differed significantly (p<0.05) from the number in the south, when tested with the non-parametric Kruskal-Wallis test. The episodes cannot be completely explained by high precipitation amounts: the mean sulphate concentration in episodic rain was higher than the annual mean concentration. The episodes were mostly imported: the air mass arriving at the station had passed over areas with high emissions outside Finland. A more exact knowledge of the episodicity benefits an examination of the ecological stress caused by acid deposition as well as a study of the critical load and the crossing of this threshold.     

Rapid time-resolved fluoroimmunoassay for the screening of narasin and salinomycin residues in poultry and eggs

Anticoccidial drugs are extensively used in the poultry industry to control the infection of the single-cell protozoa of the genus Eimeria. The most commonly used coccidiostats in poultry are the polyether ionophores such as narasin and salinomycin. This paper presents a rapid and simple method for the screening of residues of these two coccidiostatic compounds in poultry and eggs. The method is based on time-resolved fluoroimmunoassay. Sample preparation of eggs consists only of one extraction and evaporation step, and a solid phase extraction step is needed only for the muscle sample preparation. Mean recoveries were 91.0% from muscle tissue and 81.1% from eggs for both narasin and salinomycin. The performance of the assay was evaluated only for narasin because salinomycin had a cross-reactivity of 100% in the assay, and the recoveries of the compounds were not significantly different (P >0.05). The limits of detection [mean + 3 x standard deviation (SD)] of narasin were 0.56 and 0.28 microg/kg, and the limits of quantification (mean + 9 x SD) were 1.80 and 0.57 microg/kg for muscle and eggs, respectively. The coefficients of variation (CV) of the interassay precision of the method, evaluated by five replicate analyses of muscle samples spiked with 2 microg/kg of narasin and egg samples spiked with 1 microg/kg of narasin, were 4.1 and 6.4%, respectively. The CVs of intra-assay precision tests, determined by 10 replicate analyses at the above-mentioned concentration levels, were 3.8 and 4.5%, respectively.     

Isolation, structure determination, synthesis, and sensory activity of N-phenylpropenoyl-L-amino acids from cocoa (Theobroma cacao)

Application of chromatographic separation and taste dilution analyses recently revealed besides procyanidins a series of N-phenylpropenoyl amino acids as the key contributors to the astringent taste of nonfermented cocoa beans as well as roasted cocoa nibs. Because these amides have as yet not been reported as key taste compounds, this paper presents the isolation, structure determination, and sensory activity of these amino acid amides. Besides the previously reported (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-3-hydroxy-L-tyrosine (clovamide), (-)-N-[4'-hydroxy-(E)-cinnamoyl]-L-tyrosine (deoxyclovamide), and (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-tyrosine, seven additional amides, namely, (+)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-aspartic acid, (+)-N-[4'-hydroxy-(E)-cinnamoyl]-L-aspartic acid, (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-glutamic acid, (-)-N-[4'-hydroxy-(E)-cinnamoyl]-L-glutamic acid, (-)-N-[4'-hydroxy-(E)-cinnamoyl]-3-hydroxy-L-tyrosine, (+)-N-[4'-hydroxy-3'-methoxy-(E)-cinnamoyl]-L-aspartic acid, and (+)-N-[(E)-cinnamoyl]-L-aspartic acid, were identified for the first time in cocoa products by means of LC-MS/MS, 1D/2D-NMR, UV-vis, CD spectroscopy, and polarimetry, as well as independent enantiopure synthesis. Using the recently developed half-tongue test, human recognition thresholds for the astringent and mouth-drying oral sensation were determined to be between 26 and 220 micromol/L (water) depending on the amino acid moiety. In addition, exposure to light rapidly converted these [E]-configured N-phenylpropenoyl amino acids into the corresponding [Z]-isomers, thus indicating that analysis of these compounds in food and plant materials needs to be performed very carefully in the absence of light to prevent artifact formation.     

The Effect of Endotoxin on the Liver Lipid Peroxide Level and on the Liver and Plasma Zinc Concentrations in Rats As Related to Time After Administration

The lipid peroxide level of rat liver increased due to i.p. endotoxin injection, reaching its maximum, value 24 h after administration. After that the level declined, reaching approximately the initial value at 48 h. The liver Zn concentration increased and the plasma Zn concentration rapidly decreased after the injection. The liver Zn concentration then gradually declined and the plasma Zn respectively increased near the initial level 48 h after the injection.The highest lipid peroxide level occurred at 24 h when the mean Zn concentration of the plasma and liver were already relatively near the initial level, suggesting a regulative role of Zn in lipid peroxidation.     

Molecular definition of the taste of roasted cocoa nibs (Theobroma cacao) by means of quantitative studies and sensory experiments

Sensory-guided decomposition of roasted cocoa nibs revealed that, besides theobromine and caffeine, a series of bitter-tasting 2,5-diketopiperazines and flavan-3-ols were the key inducers of the bitter taste as well as the astringent mouthfeel imparted upon consumption of roasted cocoa. In addition, a number of polyphenol glycopyranosides as well as a series of N-phenylpropenoyl-l-amino acids have been identified as key astringent compounds of roasted cocoa. In the present investigation, a total of 84 putative taste compounds were quantified in roasted cocoa beans and then rated for the taste contribution on the basis of dose-over-threshold (DoT) factors to bridge the gap between pure structural chemistry and human taste perception. To verify these quantitative results, an aqueous taste reconstitute was prepared by blending aqueous solutions of the individual taste compounds in their "natural" concentrations. Sensory analyses revealed that the taste profile of this artificial cocktail was very close to the taste profile of an aqueous suspension of roasted cocoa nibs. To further narrow down the number of key taste compounds, finally, taste omission experiments and human dose/response functions were performed, demonstrating that the bitter-tasting alkaloids theobromine and caffeine, seven bitter-tasting diketopiperazines, seven bitter- and astringent-tasting flavan-3-ols, six puckering astringent N-phenylpropenoyl-l-amino acids, four velvety astringent flavonol glycosides, gamma-aminobutyric acid, beta-aminoisobutyric acid, and six organic acids are the key organoleptics of the roasted cocoa nibs.     

Chemical Characterization of Metal-Contaminated Soil in Two Study Areas in Finland

Water, Air, & Soil Pollution - In the present work we studied the role of humic acids in the heavy metal–soil interaction after the addition of different amounts of humic acids to a soil...