Reduced Face Aftereffects in Autism Are Not Due to Poor Attention

This study aimed to determine why face identity aftereffects are diminished in children with autism, relative to typical children. To address the possibility that reduced face aftereffects might reflect reduced attention to adapting stimuli, we investigated the consequence of controlling attention to adapting faces during a face identity aftereffect task in children with autism and typical children. We also included a size-change between adaptation and test stimuli to determine whether the reduced aftereffects reflect atypical adaptation to low- or higher-level stimulus properties. Results indicated that when attention was controlled and directed towards adapting stimuli, face identity aftereffects in children with autism were significantly reduced relative to typical children. This finding challenges the notion that atypicalities in the quality and/or quantity of children’s attention during adaptation might account for group differences previously observed in this paradigm. Additionally, evidence of diminished face identity aftereffects despite a stimulus size change supports an adaptive processing atypicality in autism that extends beyond low-level, retinotopically coded stimulus properties. These findings support the notion that diminished face aftereffects in autism reflect atypicalities in adaptive norm-based coding, which could also contribute to face processing difficulties in this group.     

Age-related changes in conversion of 5 alpha-androstan-17 beta-ol-3-one to 5 alpha-androstane-3 alpha,17 beta-diol and 5 alpha-androstane-3 beta,17 beta-diol by rat testicular cells in vitro

Conversion of labelled 5 alpha-androstane-17 beta-ol-3-one (DHT) by isolated testicular cells from rats of different ages was examined under saturating substrate conditions in vitro (5--10 micrograms DHT/ml in a 24 h incubation). Two detectable metabolites of DHT were produced by testicular cells in vitro. 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol) and 5 alpha-androstane-3 beta, 17 beta-diol (3 beta-diol). Production of these diols during a 24 h period was linear, and the amounts formed were directly related to the cell number. The amount of 3 alpha- and 3 beta-diols formed by testicular cells of rats of different ages increased from Day 10 to Day 25, then declined. Testicular cells from rats 10 to 20 days of age converted DHT mainly to 3 alpha-diol, but thereafter 3 beta-diol was the predominant testicular metabolite of DHT.     

Ternary complex formation on the adenovirus packaging sequence by the IVa2 and L4 22-kilodalton proteins

Assembly of infectious adenovirus particles requires seven functionally redundant elements at the left end of the genome, termed A repeats, that direct packaging of the DNA. Previous studies revealed that the viral IVa2 protein alone interacts with specific sequences in the A repeats but that additional IVa2-containing complexes observed during infection require the viral L4 22-kDa protein. In this report, we purified a recombinant form of the 22-kDa protein to characterize its DNA binding properties. In electrophoretic mobility shift assay analyses, the 22-kDa protein alone did not interact with the A repeats but it did form complexes on them in the presence of the IVa2 protein. These complexes were identical to those seen in extracts from infected cells and had the same DNA sequence dependence. Furthermore, we provide data that the 22-kDa protein enhances binding of the IVa2 protein to the A repeats and that multiple binding sites in the packaging sequence augment this activity. These data support a cooperative role of the IVa2 and 22-kDa proteins in packaging and assembly.     

Small molecule intercalation with double stranded DNA: implications for normal gene regulation and for predicting the biological efficacy and genotoxicity of drugs and other chemicals

The binding of small molecules to double stranded DNA including intercalation between base pairs has been a topic of research for over 40 years. For the most part, however, intercalation has been of marginal interest given the prevailing notion that binding of small molecules to protein receptors is largely responsible for governing biological function. This picture is now changing with the discovery of nuclear enzymes, e.g. topoisomerases that modulate intercalation of various compounds including certain antitumor drugs and genotoxins. While intercalators are classically flat, aromatic structures that can easily insert between base pairs, our laboratories reported in 1977 that a number of biologically active compounds with greater molecular thickness, e.g. steroid hormones, could fit stereospecifically between base pairs. The hypothesis was advanced that intercalation was a salient feature of the action of gene regulatory molecules. Two parallel lines of research were pursued: (1) development of technology to employ intercalation in the design of safe and effective chemicals, e.g. pharmaceuticals, nutraceuticals, agricultural chemicals; (2) exploration of intercalation in the mode of action of nuclear receptor proteins. Computer modeling demonstrated that degree of fit of certain small molecules into DNA intercalation sites correlated with degree of biological activity but not with strength of receptor binding. These findings led to computational tools including pharmacophores and search engines to design new drug candidates by predicting desirable and undesirable activities. The specific sequences in DNA into which ligands best intercalated were later found in the consensus sequences of genes activated by nuclear receptors implying intercalation was central to their mode of action. Recently, the orientation of ligands bound to nuclear receptors was found to match closely the spatial locations of ligands derived from intercalation into unwound gene sequences suggesting that nuclear receptors may be guiding ligands to DNA with remarkable precision. Based upon multiple lines of experimental evidence, we suggest that intercalation in double stranded DNA is a ubiquitous, natural process and a salient feature of the regulation of genes. If double stranded DNA is proven to be the ultimate target of genomic drug action, intercalation will emerge as a cornerstone of the future discovery of safe and effective pharmaceuticals.     

Water relations and adaptations to increasing water deficit in three perennial legumes, Medicago sativa, Dorycnium hirsutum and Dorycnium rectum

Dorycnium hirsutum (L.) Ser. and Dorycnium rectum (L.) Ser. are Mediterranean perennial legumes that may have potential as alternative forage plants to Medicago sativa (lucerne, alfalfa) for low rainfall dryland agriculture. Strategies for surviving periods of water deficit are vital for perennial plants in water-limited environments. This experiment compared leaf physiological and morphological adaptations to increasing water deficit among D. hirsutum, D. rectum and M. sativa. Plants were grown in the glasshouse in large pots (7.8 L, 1 m deep, 10 cm diameter) containing a sandy clay loam (14% available water content) to limit differences between root foraging among the species. Watering was withheld for 21 days and predawn and midday leaf water and osmotic potential were determined. Mid-morning rates of gas exchange were measured at five times as soil water was depleted. After 35 days of withholding water, plant recovery was measured. D. hirsutum and M. sativa reduced stomatal conductance at leaf water potentials below −1.8 MPa and water-stressed D. hirsutum osmotically adjusted by up to 0.68 MPa. D. rectum differed from the other species; leaf water potential was maintained at high levels until soil water content had reached low levels, and reductions in stomatal conductance and photosynthesis were not associated with leaf water potential. D. hirsutum and M. sativa displayed leaf morphological adaptations that may contribute to greater resistance of water deficit. Only one of five D. rectum plants survived the water-stress treatment compared to five of five for D. hirsutum and four of five for M. sativa. The water relations and physiology of D. hirsutum observed in this study suggest that it possesses adaptations suitable for arid environments. On the other hand, the poor survival and water relations of D. rectum indicate that it is poorly adapted to situations where water deficit is common.     

Targeted metabolomics analysis of Campylobacter coli VC167 reveals legionaminic acid derivatives as novel flagellar glycans

Glycosylation of Campylobacter flagellin is required for the biogenesis of a functional flagella filament. Recently, we used a targeted metabolomics approach using mass spectrometry and NMR to identify changes in the metabolic profile of wild type and mutants in the flagellar glycosylation locus, characterize novel metabolites, and assign function to genes to define the pseudaminic acid biosynthetic pathway in Campylobacter jejuni 81-176 (McNally, D. J., Hui, J. P., Aubry, A. J., Mui, K. K., Guerry, P., Brisson, J. R., Logan, S. M., and Soo, E. C. (2006) J. Biol. Chem. 281, 18489-18498). In this study, we use a similar approach to further define the glycome and metabolomic complement of nucleotide-activated sugars in Campylobacter coli VC167. Herein we demonstrate that, in addition to CMP-pseudaminic acid, C. coli VC167 also produces two structurally distinct nucleotide-activated nonulosonate sugars that were observed as negative ions at m/z 637 and m/z 651 (CMP-315 and CMP-329). Hydrophilic interaction liquid chromatography-mass spectrometry yielded suitable amounts of the pure sugar nucleotides for NMR spectroscopy using a cold probe. Structural analysis in conjunction with molecular modeling identified the sugar moieties as acetamidino and N-methylacetimidoyl derivatives of legionaminic acid (Leg5Am7Ac and Leg5AmNMe7Ac). Targeted metabolomic analyses of isogenic mutants established a role for the ptmA-F genes and defined two new ptm genes in this locus as legionaminic acid biosynthetic enzymes. This is the first report of legionaminic acid in Campylobacter sp. and the first report of legionaminic acid derivatives as modifications on a protein.