Automatic determination of calcium and magnesium by coulometric titration

An automatic system based on the use of a PC-compatible computer was developed for the implementation of coulometric titrations by release of EDTA from its Hg complex on electrochemical reduction of the Hg²⁺ ion. A variety of indicators electrodes were assayed to obtain potentiometric titration curves. The method thus developed allows the straightforward, convenient determination of Ca and Mg and was applied to the analysis of various real samples with good results.     

Early successional sites and the recovery of vegetation structure and tree species of the tropical dry forest in Veracruz,Mexico

Secondary successional vegetation represents one-third of the 7% of the original area covered with tropical dry forest that remains in central Veracruz, Mexico. In this region, fallow periods are short, in general, no longer than 7–10 years, and old secondary successional sites are not available. Therefore we evaluated the potential of very early successional stages of tropical dry forest with different land use histories for recovering the structure and composition of regional forest. We compared five early successional sites (7–72 months) with five nearby forest remnants. Successional sites had reached 38 and 30%, respectively, of the average basal area and density recorded for the forest understories, but only 5 and 10%, respectively, of the basal area and density of forest overstories. A total of 132 tree species were recorded, 45 at successional and 107 at forest sites. Individuals of tree species with animal-dispersed seeds (57%) were significantly better represented than wind-dispersed (22%) and self-dispersing (21%) species in both successional and forest sites. Successional sites had already recruited 10% of the intermediate and shade-tolerant species that grow in forest remnants. However, only 20 species occurred in both early successional and forest sites, several showing resprouting ability. We conclude that the entry of forest species to the successional process at very early stages and the recruitment of individuals from resprouting may facilitate the recovery of the dry forest in Veracruz.     

Influence of yeast strain and aging time on free amino acid changes in sparkling ciders

An analytical method for the determination of free amino acids in ciders is reported. It is based on high-performance liquid chromatography with an automatic precolumn derivatization with o-phthaldehyde and 3-mercaptopropionic acid and diode array detection. The method was applied to monitor the amino acids during second fermentation of sparkling ciders. This paper reports the influence of yeast strains and aging time on the amino acid composition of sparkling ciders. The application of principal component analysis enables the ciders to be differentiated on the basis of the two factors considered (yeast strain and aging time). The first principal component, which accounts for 58% of the total variance, achieved the separation according to aging time with serine, glycine, alanine, valine, ornithine, leucine, and lysine as the most important variables. The second principal component, accounting for 28% of the explained variance, is closely related to aspartic acid and asparagine and separates the samples according to the yeast strain.     

Grazing enhanced spatial heterogeneity of soil dehydrogenase activity in arid shrublands of Patagonia,Argentina

Journal of Soils and Sediments - The impacts of sheep grazing on soil microorganisms and enzyme activities are not yet fully understood in arid and semi-arid regions, despite the fact that most...     

Genetic diversity,phylogenetic position and morphometric analysis of Astacus colchicus (Decapoda,Astacidae): a new insight into Eastern European crayfish fauna

The phylogeny of European crayfish fauna, especially with respect to Eastern European species, is still far from being completely resolved. To fill this gap, we analyzed most of the European crayfish species focusing on the phylogenetic position of the endemic crayfish Astacus colchicus, inhabiting Georgia. Three mitochondrial and one nuclear marker were used to study evolutionary relationships among European crayfish species, resulting in the unique phylogenetic position of A. colchicus indicating independent species status to A. astacus. Phylogenetic analyses revealed a deep molecular divergence of A. colchicus in comparison to A. astacus (6.5–10.9% in mtDNA and 1.1% in nDNA) as well as to Pontastacus leptodactylus and P. pachypus (5.5–10.0% in mtDNA and 1.4–2.4% in nDNA). Absent ventral process on second male pleopod and abdominal somites II and III with pleura rounded lacking prominent spines clearly indicate taxonomic assignment to the genus Astacus; however, the species is distributed almost in the middle of Ponto-Caspian area typical by occurrence of the genus Pontastacus. Several morphological indices linked to head length, carapace, and total body length and width were found to demonstrate apparent differences between A. colchicus and A. astacus. Although this study provides a novel insight into European crayfish phylogeography, we also point out the gaps in comprehensive study of the P. leptodactylus species complex, which could reveal details about the potential species status of particular species and subspecies within this genus.     

Aphid Transmission Alters the Genomic and Defective RNA Populations of Citrus tristeza virus Isolates

ABSTRACT A total of 14 Spanish isolates of Citrus tristeza virus (CTV) and 1 isolate from Japan were transmitted by Aphis gossypii, and the subisolates obtained were compared with the source isolates for symptom expression and double-stranded RNA (dsRNA) pattern. Of the 14 Spanish isolates, 9 showed altered dsRNA patterns after aphid transmission but only minor variations in the intensity of symptoms induced on Mexican lime. Northern blot hybridization with complementary DNA (cDNA) probes corresponding to both the 5' and the 3' termini of the CTV genomic RNA (gRNA) showed that the dsRNA bands that could be used to discriminate between the dsRNA pattern of the source and the aphid-transmitted isolates were the replicative forms of defective RNAs (D-RNAs). Conversely, the Japanese isolate and two subisolates obtained from it by aphid transmission had the same dsRNA pattern, but one of the subisolates induced milder symptoms in several hosts. Dot-blot hybridization with cDNA probes representing several regions of the gRNA showed that most of the aphid-transmitted isolates differed from the corresponding source isolate by their hybridization pattern. Our results indicate that aphid transmission often sorts the populations of gRNA variants and D-RNAs present in CTV isolates.     

Hormonal induction of ovulation in pikeperch (Sander lucioperca L.) using human chorionic gonadotropin (hCG) and mammalian GnRH analogue

The aim of the present study was to study spawning stimulation in artificial reproduction of females pikeperch (Sander lucioperca L.) using “Chorulon” containing the human chorionic gonadotropin (hCG) and compare with “Supergestran” containing a mammalian GnRH ([D-Ala⁶]GnRHProNhet) analogue. The females were divided into eleven experimental groups and injected with hCG at 250, 500, 750, and 1 000 IU kg^?1 body weight (BW) and mGnRHa at 1, 2.5, 5, 10, 25, and 50 μg kg^?1 BW. In all treatments, a single intramuscular injection of hormone was performed. Control group was injected with 0.9 % NaCl, 0.9 cm³ kg^?1 BW. The average percentages of ovulating females were 88.5 ± 12.3 and 80.8 ± 10.9 % in hCG- and mGnRHa-treated groups, respectively. The average diameter of eggs was 0.95 ± 0.06 and 0.98 ± 0.06 mm in hCG- and mGnRHa-treated groups, respectively. Neither ovulation rate nor diameter of egg was statistically differed among hormonally treated groups. Statistical difference was observed only in hatching rate, where the average were 73.6 ± 14.4 and 50.6 ± 17.7 % in hCG and mGnRHa-treated groups, respectively. Among hormonally treated groups, the best results were observed in groups treated with hCG at 500 and 750 IU kg^?1 and in groups treated with mGnRHa at 25 μg kg^?1. No ovulation was observed in the control group. This study indicated successful ovulation in pikeperch using a single intramuscular injection of hCG or mGnRHa analogue.     

Chemical Composition and Starch Digestibility of Different Gluten-free Breads

The increasing demand for gluten-free products has favoured the design of numerous gluten-free bakery products which intended to mimic the quality characteristics of wheat bakery products. The objective of this study was to evaluate the nutritional pattern of gluten-free breads representative of the Spanish market for this type of products. The protein, fat and mineral content of the gluten-free breads showed great variation, ranging from 0.90 to 15.5 g/100 g, 2.00 to 26.1 g/100 g and 1.10 to 5.43 g/100 g, respectively. Gluten-free breads had very low contribution to the recommended daily protein intake, with a high contribution to the carbohydrate dietary reference intake. Dietary fiber content also showed great variation varying from 1.30 to 7.20 g/100 g. In vitro enzymatic hydrolysis of starch showed that the most predominant fraction was the rapidly digestible starch that varied from 75.6 to 92.5 g/100 g. Overall, gluten-free breads showed great variation in the nutrient composition, being starchy based foods low in proteins and high in fat content, with high glycaemic index.     

Impact of glyphosate application on microbial biomass and metabolic activity in a Vertic Argiudoll from Argentina

The widespread use of genetically modified crops tolerant to glyphosate, has strongly promoted the use of this herbicide. This work evaluates the effect of increasing doses of glyphosate on biomass and metabolic activity and metabolic quotient of soil microbiota under controlled conditions. Commercial formulation of glyphosate (48%) was sprayed over a Vertic Argiudoll placed in trays, at doses of 0.48, 0.96, 1.92 and 3.84 L a.i ha^?1. Doses usually applied in the field are between 0.96 and 1.92 L a.i ha^?1. Treatments and control were incubated at 25 °C and 75% of water holding capacity. After 4 and 45 days from glyphosate application, carbon from microbial biomass (C-MB), microbial respiration rate (MR), metabolic quotient (qCO₂), and dehydrogenase activity (DA) were determined. The C-MB at 4 days of incubation did not differ (P < 0.05) between the control and the doses of 0.48 and 0.96 L, while it was significantly lower in the highest doses. After 45 days, C-BM in the dose of 3.84 L was significantly lower than the control. The MR showed significant differences over the time but not between doses. Significant differences were found in qCO₂ between doses in both periods of incubation. Dehydrogenase activity was significantly higher in the treatments with glyphosate than in the control at the beginning of incubation. Treatment with 0.48 L presented the highest value after 45 days, while the dose of 3.84 L had lowest DA. The variables analyzed showed an initial inhibitory effect that affected the microbial cells. However, this effect was temporary at doses equivalent or higher than those usually applied in the field.