Anticipatory Smooth Eye Movements in Autism Spectrum Disorder

Smooth pursuit eye movements are important for vision because they maintain the line of sight on targets that move smoothly within the visual field. Smooth pursuit is driven by neural representations of motion, including a surprisingly strong influence of high-level signals representing expected motion. We studied anticipatory smooth eye movements (defined as smooth eye movements in the direction of expected future motion) produced by salient visual cues in a group of high-functioning observers with Autism Spectrum Disorder (ASD), a condition that has been associated with difficulties in either generating predictions, or translating predictions into effective motor commands. Eye movements were recorded while participants pursued the motion of a disc that moved within an outline drawing of an inverted Y-shaped tube. The cue to the motion path was a visual barrier that blocked the untraveled branch (right or left) of the tube. ASD participants showed strong anticipatory smooth eye movements whose velocity was the same as that of a group of neurotypical participants. Anticipatory smooth eye movements appeared on the very first cued trial, indicating that trial-by-trial learning was not responsible for the responses. These results are significant because they show that anticipatory capacities are intact in high-functioning ASD in cases where the cue to the motion path is highly salient and unambiguous. Once the ability to generate anticipatory pursuit is demonstrated, the study of the anticipatory responses with a variety of types of cues provides a window into the perceptual or cognitive processes that underlie the interpretation of events in natural environments or social situations.     

Strongyloidiasis in Canadian Far East war veterans

A survey was done of Canadians who had been interned by the Japanese during World War II to assess the prevalence of latent infection with Strongyloides stercoralis in this group. Packages containing three mail-in kits and a questionnaire were sent to 992 men, 694 (70%) of whom responded. Larvae were found in the stool specimens of four of the respondents. Examination of stool specimens after formalin-ether concentration was the most successful method of detecting Strongyloides larvae. The Baermann concentration technique yielded negative results in all four men. Three of the four cases of strongyloidiasis were detected after sampling of three fecal specimens. In the fourth case additional specimens were requested on the basis of data derived from the questionnaire. The most frequently cited clinical manifestations were abdominal pain, weight loss, diarrhea and rashes.     

Determination of 8-oxoguanine in human plasma and urine by high-performance liquid chromatography with electrochemical detection

A highly sensitive and selective method for determining 8-oxoguanine in plasma and urine was developed by high-performance liquid chromatography with electrochemical detection. The compound was separated by gradient elution on a C₁₈ reversed-phase column with a mobile phase of acetonitrile and 0.1 M sodium acetate, pH 5.2. 8-Hydroxy-2′-deoxyguanosine was used as internal standard. 8-Oxoguanine was detected electrochemically by setting the potential to +300 mV vs. Pd reference. The sensitivity of the assay was 22 ng/ml with a signal-to-noise ratio of 7:1. The within-day relative standard deviations for 8-oxoguanine quality control samples with concentrations of 3340, 1340 and 84 ng/ml were 3.6, 4.3 and 5.7% for plasma, and 4.1, 4.6 and 6.2% for urine, respectively. The day-to-day relative standard deviations for the same samples were 3.8, 6.8 and 7.1% for plasma, and 3.9, 7.0 and 7.9% for urine, respectively. The method is designed to study the pharmacokinetics and metabolic fate of O⁶-benzylguanine in a phase I clinical trial. Previously, O⁶-benzyl-8-oxoguanine was identified as the primary metabolite of O⁶-benzylguanine in humans. We now demonstrate that 8-oxoguanine is a further metabolite of O⁶-benzylguanine.     

Separate Intramolecular Targets for Protein Kinase A Control N-Methyl-d-aspartate Receptor Gating and Ca2+ Permeability

Protein kinase A (PKA) enhances synaptic plasticity in the central nervous system by increasing NMDA receptor current amplitude and Ca²⁺ flux in an isoform-dependent yet poorly understood manner. PKA phosphorylates multiple residues on GluN1, GluN2A, and GluN2B subunits in vivo, but the functional significance of this multiplicity is unknown. We examined gating and permeation properties of recombinant NMDA receptor isoforms and of receptors with altered C-terminal domain (CTDs) prior to and after pharmacological inhibition of PKA. We found that PKA inhibition decreased GluN1/GluN2B but not GluN1/GluN2A gating; this effect was due to slower rates for receptor activation and resensitization and was mediated exclusively by the GluN2B CTD. In contrast, PKA inhibition reduced NMDA receptor-relative Ca²⁺ permeability (P_Ca/P_Na) regardless of the GluN2 isoform and required the GluN1 CTD; this effect was due primarily to decreased unitary Ca²⁺ conductance, because neither Na⁺ conductance nor Ca²⁺-dependent block was altered substantially. Finally, we show that both the gating and permeation effects can be reproduced by changing the phosphorylation state of a single residue: GluN2B Ser-1166 and GluN1 Ser-897, respectively. We conclude that PKA effects on NMDA receptor gating and Ca²⁺ permeability rely on distinct phosphorylation sites located on the CTD of GluN2B and GluN1 subunits. This separate control of NMDA receptor properties by PKA may account for the specific effects of PKA on plasticity during synaptic development and may lead to drugs targeted to alter NMDA receptor gating or Ca²⁺ permeability.     

Both developmental and metabolic signals activate the promoter of a class I patatin gene

Patatin is one of the major soluble proteins in potato tubers and is encoded by a multigene family. Based on structural considerations two classes of patatin genes are distinguished. The 5′-upstream regulatory region of a class I gene contained within a 1.5 kb sequence is essential and sufficient to direct a high level of tuber-specific gene activity which was on average 100- to 1000-fold higher in tubers as compared to leaf, stem and roots in greenhouse grown transgenic potato plants when fused to the β-glucuronidase reporter gene. Histochemical analysis revealed this activity to be present in parenchymatic tissue but not in the peripheral phellem cells of transgenic tubers. Furthermore the promoter fragment can be activated in leaves under conditions that simulate the need for the accumulation of starch in storage organs, i.e. high levels of sucrose. The expression is restricted to both mesophyll and epidermal cells in contrast to vascular tissue or hair cells.     

DoesAgapetus fuscipes cultivate algae in its case?

The presence of algae within the cases ofAgapetus fuscipes was investigated. Cases recognised as dirty or clean with the naked eye had more and less algal growth, respectively. Larvae in the former survived significantly longer when starved in the laboratory. It is suggested that the presence of algae within the cases would be of ecological advantage during periods of flood.     

Isolation and characterization of a sucrose carrier cDNA from spinach by functional expression in yeast.

Active loading of the phloem with sucrose in leaves is an essential part of the process of supplying non-photosynthetic tissues with carbon and energy. The transport is protein mediated and coupled to proton-symport, but so far no sucrose carrier gene has been identified. Using an engineered Saccharomyces cerevisiae strain, a cDNA from spinach encoding a sucrose carrier was identified by functional expression. Yeast strains that allow the phenotypic recognition of a sucrose carrier activity were constructed by expressing a cytoplasmic invertase from yeast, or the potato sucrose synthase gene, in a strain unable to transport or grow on sucrose due to a deletion in the SUC2 gene. A spinach cDNA expression library established from the poly(A)+ RNA from source leaves of spinach and cloned in a yeast expression vector yielded transformed yeast clones which were able to grow on media containing sucrose as the sole carbon source. This ability was strictly linked to the presence of the spinach cDNA clone pS21. Analysis of the sucrose uptake process in yeast strains transformed with this plasmid show a pH-dependent uptake of sucrose with a Km of 1.5 mM, which can be inhibited by maltose, alpha-phenylglucoside, carbonyl cyanide m-chlorophenylhydrazone and p-chloromercuribenzenesulfonic acid. These data are in accordance with measurements using both leaf discs and plasma membrane vesicles from leaves of higher plants. DNA sequence analysis of the pS21 clone reveals the presence of an open reading frame encoding a protein with a molecular mass of 55 kDa. The predicted protein contains several hydrophobic regions which could be assigned to 12 membrane-spanning regions.(ABSTRACT TRUNCATED AT 250 WORDS)     

A detailed study of the regulation and evolution of the two classes of patatin genes in Solanum tuberosum L.

The class-specific expression of patatin genes was investigated by analysing four new patatin genes. A class I patatin gene from cv. Berolina as well as a class I and two class II patatin genes from the monohaploid cultivar AM 80/5793 were isolated and partially sequenced. Sequence comparison indicates rearrangements as the major source for the generation of diversity between the different members of the classes. The expression of single genes was studied in potato plants transformed with chimaeric genes where the putative patatin promoters were fused to the GUS reporter gene. A detailed histochemical analysis reveals that both class I genes are expressed as the previously described class I patatin gene B33 from cv. Berolina [1], i.e. in the starch-containing cells of potato tubers and in sucrose-induced leaves. The class II gene pgT12 shows the same pattern as the previously described class II gene pgT2 [2], i.e. expression in root tips and in the vascular tissue of tubers, whereas no activity was detectable for pgT4. Thus the expression pattern of both classes of genes seems to be stable at least within or even between different cultivars.