Background-Attention-deficit hyperactivity disorder (ADHD) is one of the most common and highly heritable child psychiatric disorders. There is strong evidence that children with ADHD show slower and more variable responses in tasks such as Go/Nogo tapping aspects of executive functions like sustained attention and response control which may be modulated by motivational factors and/or state-regulation processes. The aim of this study was (1) to determine if these executive functions may constitute an endophenotype for ADHD; (2) to investigate for the first time whether known modulators of these executive functions may also be familial and (3) to explore whether gender has an impact on these measures.

The accumulation of carotenoids in higher plants is regulated by the environment, tissue type and developmental stage. In Brassica napus leaves, beta-carotene and lutein were the main carotenoids present while petals primarily accumulated lutein and violaxanthin. Carotenoid accumulation in seeds was developmentally regulated with the highest levels detected at 35-40 days post anthesis. The carotenoid biosynthesis pathway branches after the formation of lycopene. One branch forms carotenoids with two beta rings such as beta-carotene, zeaxanthin and violaxanthin, while the other introduces both beta- and epsilon-rings in lycopene to form alpha-carotene and lutein. By reducing the expression of lycopene epsilon-cyclase (epsilon-CYC) using RNAi, we investigated altering carotenoid accumulation in seeds of B. napus. Transgenic seeds expressing this construct had increased levels of beta-carotene, zeaxanthin, violaxanthin and, unexpectedly, lutein. The higher total carotenoid content resulting from reduction of epsilon-CYC expression in seeds suggests that this gene is a rate-limiting step in the carotenoid biosynthesis pathway. epsilon-CYC activity and carotenoid production may also be related to fatty acid biosynthesis in seeds as transgenic seeds showed an overall decrease in total fatty acid content and minor changes in the proportions of various fatty acids.

The substrate specificity and regioselectivity of the Brassica napus extraplastidial linoleate desaturase (FAD3) was investigated in vivo in a heterologous expression system. A strain of the yeast Saccharomyces cerevisiae producing the plant enzyme was constructed and cultured in media containing a variety of fatty acids. The products of desaturation of these potential substrates were determined by gas chromatographic and mass spectrometric analysis of the yeast cultures. The results indicate that the enzyme has: (a) -3, as opposed to ⌬-15 or double-bond-related regioselectivity, (b) the ability to desaturate substrates in the 16 to 22 carbon range, (c) a preference for substrates with -6 double bonds, but the ability to desaturate substrates with -6 hydroxyl groups or -9 or -5 double bonds, and (d) a relative insensitivity to double bonds proximal to the carboxyl end of the substrate.

S locus glycoprotein (SLG) and S locus receptor kinase (SRK) cDNAs were isolated from an S allele present in a number of self-compatible Brassica napus lines. This Aí0 allele did not segregate with self-incompatibility in crosses involving other self-incompatible B. napus lines. The SLG-Aí0 cDNA was found to contain an intact open reading frame and was predicted to encode an SLG protein with sequence similarities to those previously associated with phenotypically strong self-incompatibility reactions. SLG-Aí0 transcripts were detected in the developing stigma at steady state levels even higher than those detected for SLG alleles linked with self-incompatibility. Analysis of the corresponding SRK-Aí0 cDNA showed that it was very similar to other S locus receptor kinase genes and was expressed predominantly in the stigma.However, a l-bp deletion was detected in the SRK gene toward the 3' end of the SLG homology domain. This deletion would lead to premature termination of translation and'the production of a truncated SRK protein. The A10 allele was determined to represent a R oleracea S allele based on its segregation pattern with the R oleracea SZ4 allele when both these alleles were present in the same B. napus background. These results suggest that a functional SRK gene is required for Brassica self-incompatibility.

A sulf ite-reductase-type protein was purified from the hyperthermophilic crenarchaeote Pyrobaculum islandicum grown chemoorganoheterotrophically with thiosulfate as terminal electron acceptor. In common with dissimilatory sulfite reductases the protein has an a#* structure and contains high-spin sirohaem, non-haem iron and acid-labile sulfide. The oxidized protein exhibits absorption maxima a t 280,392, 578 and 710 nm with shoulders a t 430 and 610 nm. The isoelectric point of pH 8 4 sets the protein apart from all dissimilatory sulfite reductases characterized thus far. The genes for the a-and P-subunits (dsrA and dsrB) are contiguous in the order dsrAdsrB and most probably comprise an operon with the directly following dsrG and dsrC genes. dsrG and dsrC encode products which are homologous to eukaryotic glutathione S-transferases and the proposed y-subunit of Desulfovibrio vulgaris sulf ite reductase, respectively. dsrA and dsrB encode 44.2 kDa and 41.2 kDa peptides which show significant similarity to the two homologous subunits DsrA and DsrB of dissimilatory sulfite reductases. Phylogenetic analyses indicate a common protogenotic origin of the P. islandicum protein and the dissimilatory sulfite reductases from sulfate-reducing and sulfideoxidizing prokaryotes. However, the protein from P. islandicum and the sulfite reductases f rom sulfate-reducers and from sulf ur-oxidizers most probably evolved into three independent lineages prior to divergence of archaea and bacteria.