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A Aguiar

Publications and source records attributed to A Aguiar.

15 recordsLinked to original sources
PubMed2007

Metal-chelating compounds produced by ectomycorrhizal fungi collected from pine plantations.

AIMS: To investigate the in vitro production of metal-chelating compounds by ectomycorrhizal fungi collected from pine plantations in southern Chile. METHODS AND RESULTS: Scleroderma verrucosum, Suillus luteus and two isolates of Rhizopogon luteolus were grown in solid and liquid modified Melin-Norkans (MMN) media with and without iron addition and the production of iron-chelating compounds was determined by Chrome Azurol S (CAS) assay. The presence of hydroxamate and catecholate-type compounds and organic acids was also investigated in liquid medium. All isolates produced iron-chelating compounds as detected by CAS assay, and catecholates, hydroxamates as well as oxalic, citric and succinic acids were also detected in all fungal cultures. Scleroderma verrucosum produced the greatest amounts of catecholates and hydroxamates whereas the highest amounts of organic acids were detected in S. luteus. Nevertheless, the highest catecholate, hydroxamate and organic acid concentrations did not correlate with the highest CAS reaction which was observed in R. luteolus (Yum isolate). CONCLUSIONS: Ectomycorrhizal fungi produced a variety of metal-chelating compounds when grown in liquid MMN medium. However, the addition of iron to all fungi cultures reduced the CAS reaction, hydroxamate and organic acid concentrations. Catecholate production was affected differently by iron, depending on the fungal isolate. SIGNIFICANCE AND IMPACT OF THE STUDY: The ectomycorrhizal fungi described in this study have never been reported to produce metal-chelating compound production. Moreover, apart from some wood-rotting fungi, this is the first evidence of the presence of catecholates in R. luteolus, S. luteus and S. verrucosum cultures.

Basidiomycota↗
PubMed1999

2.5-month-old infants' reasoning about when objects should and should not be occluded.

The present research examined 2.5-month-old infants' reasoning about occlusion events. Three experiments investigated infants' ability to predict whether an object should remain continuously hidden or become temporarily visible when passing behind an occluder with an opening in its midsection. In Experiment 1, the infants were habituated to a short toy mouse that moved back and forth behind a screen. Next, the infants saw two test events that were identical to the habituation event except that a portion of the screen's midsection was removed to create a large window. In one event (high-window event), the window extended from the screen's upper edge; the mouse was shorter than the bottom of the window and thus did not become visible when passing behind the screen. In the other event (low-window event), the window extended from the screen's lower edge; although the mouse was shorter than the top of the window and hence should have become fully visible when passing behind the screen, it never appeared in the window. The infants tended to look equally at the high- and low-window events, suggesting that they were not surprised when the mouse failed to appear in the low window. However, positive results were obtained in Experiment 2 when the low-window event was modified: a portion of the screen above the window was removed so that the left and right sections of the screen were no longer connected (two-screens event). The infants looked reliably longer at the two-screens than at the high-window event. Together, the results of Experiments 1 and 2 suggested that, at 2.5 months of age, infants possess only very limited expectations about when objects should and should not be occluded. Specifically, infants expect objects (1) to become visible when passing between occluders and (2) to remain hidden when passing behind occluders, irrespective of whether these have openings extending from their upper or lower edges. Experiment 3 provided support for this interpretation. The implications of these findings for models of the origins and development of infants' knowledge about occlusion events are discussed.

Analysis of Variance↗
PubMed1998

[CHARGE association].

Posterior choanal atresia is a congenital malformation which can occur isolated or in combination to additional malformations. In CHARGE association the other anomalies are: coloboma, heart disease, retarded development/growth or central nervous system abnormalities, genital hypoplasia or hypogonadism and ear abnormalities or deafness. The authors present three cases of CHARGE association and they also review the clinical findings required for the diagnosis.

Abnormalities, Multiple↗
PubMed1998

Eight-and-a-half-month-old infants' reasoning about containment events.

The present research examined whether 8.5-month-old infants take into account the width and compressibility of an object when determining whether it can be inserted into a container. The infants in Experiment 1 saw 2 test events. At the start of each event, a tall container rested on the apparatus floor. Next, the container was hidden by a screen, and a large ball attached to the lower end of a rod was introduced into the apparatus and lowered behind the screen into the container. Finally, the screen was removed to reveal the ball's rod protruding above the container's rim. The only difference between the 2 test events had to do with the width of the containers: in 1 event (large-container event), the container was slightly wider than the ball; in the other event (small-container event), the container was only half as wide as the ball, so that it should have been impossible for the ball to be lowered into it. Infants in a control condition saw identical test events except that a small ball was used that could fit into either the large or the small container. The infants in the experimental condition looked reliably longer at the small- than at the large-container event, whereas those in the control condition tended to look equally at the 2 events. These results suggested that, although the infants never saw the ball and the container simultaneously, they realized that the large ball could fit into the large but not the small container, whereas the small ball could fit into both containers. In Experiment 2, the large ball used in Experiment 1 was replaced with an equally large but compressible ball. The results were negative, suggesting that the infants understood that the large compressible ball could be inserted into either the small or the large container. Finally, Experiment 3 confirmed the results of the experimental condition in Experiment 1, with a slightly different procedure. Together, the present results indicate that, by 8.5 months of age, infants are already capable of sophisticated reasoning about containment events.

Attention↗
PubMed1997

Analysis of the allelic diversity of a (CA)n repeat polymorphism among alpha 1-antitrypsin gene products from northern Portugal.

The level of molecular heterogeneity associated with alpha 1-antitrypsin gene products was assessed in the population of northern Portugal using three restriction fragment length polymorphisms (RFLPs) corresponding to specific amino acid substitutions and a highly variable (CA)n repeat polymorphism located at the 5' end of the PI gene. The allelic affinities inferred from the analysis of the DNA polymorphisms essentially agree with the evolutionary pattern proposed for the PI gene products on the basis of their amino acid sequences. PI*Z can be considered the most recent common PI allele and was found to be associated with the same predominant haplotype previously reported in northern European populations, thus confirming the hypothesis that most European Z alleles are derived from a single mutation. However, a rare deficient variant that is the likely result of a recurrent Z mutation on an M2 or M4 background was additionally observed. PIS was also found to be associated with a strongly predominant haplotype and seems to be the second most recent PI common allele, while M2 and M3 show weaker associations, suggesting more ancient origins of their corresponding mutations. M1Ala213 and M1Vat213 display more homogeneous (CA)n allele frequency distributions, M1Ala213 representing the most ancient PI allele as inferred from its highest variance in (CA)n allele length.

Alleles↗
PubMed1984

Uncombable hair.

Explore the source record for details and available documents.

Child, Preschool↗
PubMed1979

Proton-nuclear-magnetic-resonance/pH-titration studies of the histidines of pancreatic phospholipase A2.

The study by means of 1H nuclear magnetic resonance (NMR) of the histidines of phospholipase A2 isolated from porcine, bovine and equine pancreas is reported. Assignment of the histidine resonances was achieved by comparison of different enzymes and the use of paramagnetic probes. pH titration curves for various histidyl resonances were obtained and compared in the presence and absence of calcium. Calcium is shown to lower the pKa of the active site histidine. The NMR results are compared with the known X-ray three-dimensional structure for the bovine enzyme.

Amino Acid Sequence↗