Determination of cadmium at ultra-trace levels by CPE–molecular fluorescence combined methodology

A highly sensitive micelle-mediated extraction methodology for the preconcentration and determination of trace levels of cadmium by molecular fluorescence has been developed. Metal was complexed with o-phenanthroline (o-phen) and eosin (eo) at pH 7.6 in buffer Tris medium and quantitatively extracted into a small volume of surfactant-rich phase of PONPE 7.5 after centrifugating. The chemical variables affecting cloud point extraction (CPE) were evaluated and optimized. The RSD for six replicates of cadmium determinations at 0.84 μg L⁻¹ level was 1.17%. The linearity range using the preconcentration system was between 2.79 × 10⁻³ μg L⁻¹ and 2.81 μg L⁻¹ with a correlation coefficient of 0.99. Under the optimal conditions, it obtained a LOD of 8.38 × 10⁻⁴ μg L⁻¹ and LOQ of 2.79 × 10⁻³ μg L⁻¹. The method presented good sensitivity and selectivity and was applied to the determination of trace amounts of cadmium in commercially bottled mineral water, tap water and water well samples with satisfactory results. The proposed method is an innovative application of CPE-luminescence to metal analysis comparable in sensitivity and accuracy with atomic spectroscopies.     

An inexpensive system for underwater video surveys of demersal fishes

A system for visual surveys of bottom fishes, assembled from readily available components, is described. A camera and a depth sounder transducer are mounted on a towed body. The camera captures the images, and the depth sounder measures the distance between the camera and the bottom. A video recorder is used to record the data—the video channel for the image, and the audio channel for distance information, which is dictated from the depth sounder display into a microphone. A relationship between distance and magnification is used to estimate the width of the survey path and the size of surveyed objects. A comparison of round goby (Apollonia melanostoma) density estimated by repeated seining and use of the underwater visual apparatus showed that the smallest individuals are underrepresented by the visual assessment, but the visual method detects about 85% of the 50 mm TL or larger gobies.     

Morphological,Physicochemical and Structural Characteristics of Oxidized Barley and Corn Starches

Barley starch was oxidized to different levels and the morphological, physicochemical and structural of the resultant oxidized barley starch were determined and compared with oxidized corn starch at the same oxidation level. The amylose content in oxidized starches decreased with increasing oxidation level, and the extent of decrease was similar for both starch types. No evidences of alteration in morphology and X‐ray diffraction pattern were noted after oxidation. The crystallinity of barley starch increased with increasing oxidation but corn starch displayed a reduced crystallinity at 5% NaOCl. The onset and peak gelatinization temperatures of oxidized starches as measured by differential scanning calorimetry showed a slight increase up to 3% NaOCl and then decreased at 5% NaOCl, whereas gelatinization enthalpy gradually decreased with increasing oxidation level. The melting temperature of retrograded oxidized starches increased with increasing oxidation. Both amylose and amylopectin were degraded during oxidation, but a higher degradation in both components as determined by high‐performance size‐exclusion chromatography (HPSEC) was noted for barley starch than for corn starch. Results of amylopectin chain‐length distribution showed that the proportions of A and B1 chains significantly increased while that of B2+ chains significantly decreased. These results suggest that differences in the structure of barley and corn starches affected their responses to oxidation. Barley starch seemed to be more susceptible to oxidation with more significant reduction in pasting temperature, viscosity, and molecular size than corn starch.     

Children's early approaches to learning and academic trajectories through fifth grade.

Children's early approaches to learning (ATL) enhance their adaptation to the demands they experience with the start of formal schooling. The current study uses individual growth modeling to investigate whether children's early ATL, which includes persistence, emotion regulation, and attentiveness, explain individual differences in their academic trajectories during elementary school. Using data from the Early Childhood Longitudinal Study – Kindergarten Cohort (ECLS-K), the present investigation examined the association between ATL at kindergarten entry and trajectories of reading and math achievement across 6 waves of data from kindergarten, 1st, 3rd, and 5th grade (n = 10,666). The current study found a positive link between early ATL and individual trajectories of reading and math performance. Overall, children's early ATL was equally beneficial for children regardless of their race/ethnicity and dimensions of their socioeconomic background. However, links between early ATL and academic trajectories differed by their gender and initial levels of math and reading achievement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A cluster analysis of the relationship between sucking habits,consistency of food ingested,and taste sensitivity in children

As sucking habits and eating behavior may be interrelated and also associated with taste, body composition, and sociodemographic factors, the objective was to perform an exploratory analysis to identify groups of children with a high degree of association between intragroup subjects, providing explanation and interpretation of the data. The study initially included 352 prepubertal children (197 girls; 7‐ to 11‐year‐old), from whom information about sociodemographic characteristics, duration of breastfeeding, past bottle‐feeding and non‐nutritive sucking habits, taste sensitivity, body mass index (BMI), and consistency of food ingested were collected. Salivary concentrations of amylase and total protein were also determined. Data were submitted to cluster analysis (hierarchical analysis, K‐means, and silhouette plot), one‐way ANOVA and correlation tests. Cluster analysis included 159 children, generating three reliable and meaningful clusters: Cluster 1 (labeled “good tasters”), was characterized by older children and higher taste sensitivity; Cluster 2 (“softer food consistency”) by longer bottle‐feeding duration and children who eat food with lower consistency, and Cluster 3 (“breastfed”) by longer breastfeeding duration (silhouette coefficient = 0.61). Cluster 3 also showed the higher percentage of normal‐weight children, normal delivery, maternal schooling, and lower rate of past non‐nutritional sucking habit. No correlation was found between salivary amylase and total protein concentrations, taste sensitivity and BMI, although taste sensitivity showed to be higher among girls (p = 0.002; power = 88%). The study identified three clusters, highlighting the relationship between nutritional sucking habits, consistency of food ingested, and sociodemographic characteristics. Most importantly, a close relation between bottle‐feeding and consumption of soft food consistency was observed.     

Structure and distribution of sensilla on maxillary palps and labella of Lutzomyia longipalpis (Diptera: Psychodidae) sand flies

The typology, number, size, and distribution pattern of labellar and palpal sensilla of male and female Lutzomyia longipalpis (Lutz and Neiva, 1912) sand flies were analyzed by scanning electron and light microscopy, contributing to the construction of a gustatory and olfactory map in this important vector species. About 35 trichoid sensilla, sorted into three different classes according to their lengths, are present on the two labellar lobes. Five distinct structures are observed in the maxillary palps, which could be classified as noninnervated (microtrichia and scales) or the following innervated structures: 1) campaniform sensilla, found near the distal end of palpal segments II and III; 2) multiporous capitate peg sensilla, found in reduced number (1-6) on segment II, but located in a group of 15-25 on the distal third part of segment III; and 3) trichoid sensilla, distributed linearly on segment IV and spirally on segment V. Light microscopy analysis of silver-stained specimens indicated the presence of pores in the trichoid sensilla and their chemosensory function is discussed, as well as the possible function of the other sensilla.     

Supercritical fluid extraction of potential migrants from paper and board intended for use as food packaging materials

The optimization of supercritical fluid extraction using CO2 for the extraction of contaminants in 15 samples of recycled paper and board (P&B) has been studied. An experimental design was used for simultaneous optimization of the variables involved in both the extraction step and the collection of the extract. Methanol was used as modifier. Several plastisizers such as diethyl phthalate, diisobutyl phthalate, di-n-butyl phthalate, dioctyl adipate, and diethylhexyl phthalate (from 2 to 100 microg/g of paper) were found in the recycled P&B samples. A discriminate analysis applied to all results obtained allow us to classify the samples in three different groups according to the content of recycled pulp (0, 10-30, and > 80% of recycled pulp), the sample thickness (from <300 to >600 microm), and the surface treatment of the paper. The analytical behavior and the results are discussed.     

Prevalence of Cyclospora sp., Cryptosporidium sp, microsporidia and fecal coliform determination in fresh fruit and vegetables consumed in Costa Rica

The presence of Cyclospora sp., Cryptosporidium sp. and microsporidia and the levels of fecal coliforms were determined in lettuce, parsley, cilantro, strawberries and blackberries acquired in local agricultural markets of the Central Valley of Costa Rica, in order to establish the possible transmission risk of these microorganisms and other pathogens from the consumption of these raw products. During the second semester of 2001 and the first of 2002, 50 different samples of each product, 25 taken in the dry season and 25 in the rainy season and coming from five different local agricultural markets were evaluated. The fecal coliforms count was done according to the technique recommended by Vanderzant & Splittstoesser. The parasite determination was done using Zielh Nielsen and Weber staining techniques from a sediment obtained through the rinse of the mentioned products, using sterile peptonated water 0.1% and centrifuging at 900 G for 15 min. One hundred per cent of vegetable samples had fecal coliforms and the greatest prevalence was obtained during the rainy season. Although all vegetables presented fecal coliforms in high concentrations, lettuce and cilantro presented statistical difference between rainy and dry season, being greater during the rainy season. Fecal coliforms were not detected in strawberries and blackberries probablydue to its low pH. All products evaluated presented, at least once, Cryptosporidium sp., Cyclospora sp. and microsporidia, showing the risk they represent to Public Health. Cryptosporidium was present in all products but strawberries. Microsporidia was present in all products except blackberries and Cyclospora was only isolated from lettuce during the dry season. These results show the importance of introducing in the country Good Agricultural Practices, especially due to the resistance of Cryptosporidium and Cyclospora to disinfecting agents.     

Temporal and topographic ultrastructural alterations of rat heart myofibrils caused by thyroid hormone

In order to further our understanding regarding the temporal and topographic ultrastructural aspects of the myocardium under thyrotoxicosis, thyroxine (T4; 25 and 100 microg/100 g bw) was administered to young rats 24 hours after birth until 15 days. The animals were then sacrificed, the hearts excised and weighed, and the ventricle tissue samples were then processed for confocal and transmission electron microscopy. At 48/72 hours and 1 week after initiation of T4 treatment with 100 microg/100 g bw, numerous lamellar bodies (probably formed by phospholipids) progressively accumulated in the heart. These bodies were observed in the cytosol, inside mitochondria and in the extracellular matrix. At 2 weeks of T4 treatment with 100 microg/100 g bw, lamellar bodies were virtually absent. Changes in cell shape, disorganization of intercellular junctions, and substantial myofibrillar disarray were observed in many cardiomyocytes. A gradient of myofibrillar disarray, which increased in abundance and intensity from the endocardium to the epicardium, was also observed. Immunocytochemical staining for desmin showed that the arrangement of this protein was disorganized in many cells of T4-treated rats as compared with normal ones, confirming ultrastructural data. The predominant appearance of myofibrillar disarray, associated with disorganization of cytoskeletal proteins in the deep myocardium, may be due to higher mechanical wall stress and consequent higher metabolic demand. Alternatively, differential sensitivity of cardiomyocytes to thyroid hormone in different areas is also a possibility.