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Like many other organic ligands, amine-based complexing agents in analytical chemistry have demonstrated substantial improvements in sensitivity and selectivity in determining metals by flame-atomic absorption spectrometry (FAAS) and electrothermal atomisation atomic absorption spectrometry (ETAAS). Amines represent a particular case for diverse potential complexing agents owing to the lone pair electrons in the nitrogen atom being capable of forming dative covalent bonds. Amines can analytically generate useful pH-dependent green switchable solvents. In this context, this work aims to critically review the diverse uses of amines in the FAAS/ETAAS fields in a comprehensive manner by mainly focusing on their effects on the atomisation processes, their behaviour as complexing agents and their possible direct and indirect determination by the AAS techniques. Various theoretical topics related to the solvent extraction processes involving amines also enhance the usefulness of this kind of compound for the AAS techniques. Further, extrapolating their usefulness in combination with other analytical techniques is straightforward. [ABSTRACT FROM AUTHOR]

This study evaluated anatomic and physiological modifications in Panicum aquaticum plants related to cadmium (Cd) tolerance. The plants were cultivated in a nutritive solution, with addition of increasing concentration of Cd. The following parameters were analyzed: absorption, translocation, concentration and Cd accumulation, growth, gas exchanges, activity of the antioxidant system, and anatomy of roots and leaves. Absorption and Cd concentration increased throughout the treatments, while accumulation and Cd translocation did not vary, due to maintenance of the biomass. Gas exchanges were not affected by Cd. Specific foliar area increased in the presence of the metal, and might be related to the reduction in leaf blade thickness and chlorophyllic parenchyma. Modifications in stomatal characteristics did not negatively affect gas exchanges. An increase in the exodermis and endodermis thickness restricted Cd translocation to the aerial part, avoiding damages to the photosynthetic system. Activity of the ascorbate peroxidase and catalase in the root contributed to a reduction in the metal toxicity. P. aquaticum presented an efficient capacity for Cd absorption, but restricted translocation. Cd accumulation was higher in the roots. Anatomic and physiological responses show a tolerance of the species to Cd in the evaluated concentrations. [ABSTRACT FROM AUTHOR]

Root cortical aerenchyma (RCA) is suggested to reduce metabolic cost for root growth, but it might lower water uptake by plants. The objective of this work was to evaluate the effects of drought and phosphorus on the RCA development along the root axis and to elucidate its role in water stress tolerance of two maize genotypes. Plants of drought-tolerant DKB390 and drought-sensitive BRS1010 genotypes were grown in Vermiculite at field capacity of 100, 75, 50, and 25 % and supplied with 0.1, 0.4, and 0.8 mM phosphorus. Growth parameters, RCA, and plant P content were evaluated for all plants. Higher RCA development was observed in DKB390 than in BRS1010. Drought reduced the percentage of RCA in the root-hair zone of both genotypes but increased its development in the root maturation zone. Phosphorus limitation enhanced RCA development only in the DKB390. Under drought stress, DKB390 showed resilient growth whereas growth was inhibited in BRS1010. Higher root P content was related to its higher supply. Therefore, RCA formation was induced either by drought or by phosphorus limitation, while no interaction was evident. The RCA development varied along the root axis in order to balance water and phosphorus uptake and the drought response was genotype dependent. [ABSTRACT FROM AUTHOR]

The polymorphic merozoite surface protein-2 (MSP-2) of Plasmodium falciparum is a major malaria-vaccine candidate. In the present study, PCR and hybridization with allelic-specific probes were used to type the Msp-2 gene from isolates from hypo-endemic Brazil (N = 113), meso-endemic Vietnam (N = 208) and holo-endemic Tanzania (N = 67). The typing methods were designed to group isolates into the dimorphic allelic families FC27 and IC1 and to detect possible between-family recombination events. The analysis was complemented by a comparison of 156 Msp-2 sequences from the GenBank database with 12 additional sequences obtained during the present study. Statistically significant differences were detected in pair-wise comparisons of the distribution of Msp-2 allelic types in Brazil and Vietnam, and in Brazil and Tanzania, but not in Vietnam and Tanzania. The extent of allelic diversity in the Msp-2 gene, as estimated by the total number of different alleles found in a given parasite population and the mean multiplicity of infections, clearly paralleled the levels of malaria endemicity in the study areas. However, no correlation between age and multiplicity of infections was found in the subjects. The patterns of Msp-2 diversity in Brazil appeared to be temporally stable, since no significant difference was observed in the distribution of Msp-2 allelic types among isolates collected, 10-13 years apart, in the same area of Rondônia. Despite the extensive sequence diversity found in Msp-2 alleles, especially in the central repetitive region of the molecule, several instances of identical or nearly identical alleles were found among isolates from different countries and regions, possibly as a result of extensive homoplasy. No recombinant allele was detected by molecular typing in any of the study sites, and the GenBank database included only 12 recombinant sequences (representing 7% of all reported Msp-2 sequences), all of them with an IC1-type 5' end and an FC27-type 3' end. A single, putative, crossover site was characterised for all recombinant alleles. Most of the allelic diversity observed was therefore attributable to variation in the repetitive region of the gene, instead of recombination between alleles of dimorphic families (as commonly found, for example, in the Msp-1 gene). The implications of these findings for studies on the genetic and antigenic diversity of malarial parasites are discussed. [ABSTRACT FROM AUTHOR]