Zebrafish have become a popular organism for the study of vertebrate gene function1,2. The virtually transparent embryos of this species, and the ability to accelerate genetic studies by gene knockdown or overexpression, have led to the widespread use of zebrafish in the detailed investigation of vertebrate gene function and increasingly, the study of human genetic disease3–5. However, for effective modelling of human genetic disease it is important to understand the extent to which zebrafish genes and gene structures are related to orthologous human genes. To examine this, we generated a high-quality sequence assembly of the zebrafish genome, made up of an overlapping set of completely sequenced large-insert clones that were ordered and oriented using a high-resolution high-density meiotic map. Detailed automatic and manual annotation provides evidence of more than 26,000 protein-coding genes6, the largest gene set of any vertebrate so far sequenced. Comparison to the human reference genome shows that approximately 70% of human genes have at least one obvious zebrafish orthologue. In addition, the high quality of this genome assembly provides a clearer understanding of key genomic features such as a unique repeat content, a scarcity of pseudogenes, an enrichment of zebrafish-specific genes on chromosome 4 and chromosomal regions that influence sex determination.

Clinical observations support a central role of the dopamine system in restless legs syndrome (RLS) but previous imaging studies of striatal dopamine D2-receptors have yielded inconclusive results. Extrastriatal dopaminergic function has hitherto not been investigated. Sixteen RLS patients naïve to dopaminergic drugs and sixteen matched control subjects were examined with PET. [11C]Raclopride and [11C]FLB 457 were used to estimate D2-receptor availability in striatum and extrastriatal regions, respectively. Examinations were performed both in the morning (starting between 10:00 and 12:00 h) and evening (starting at 18:00 h). Measures were taken to monitor and control for head movement during data acquisition. In the striatum, patients had significantly higher [11C]raclopride binding potential (BP) values than controls. In extrastriatal regions, [11C]FLB 457 BP was higher in patients than controls, and in the regional analysis the difference was statistically significant in subregions of thalamus and the anterior cingulate cortex. The diurnal variability in BP with [11C]FLB 457 and [11C]raclopride was within the previously reported test-retest reproducibility for both radioligands. The study supports involvement of the dopamine system in both striatal and extrastriatal brain regions in the pathophysiology of RLS. The brain regions where differences in D2-receptor binding were shown are implicated in the regulation of affective and motivational aspects of sensory processing, suggesting a possible pathway for sensory symptoms in RLS. Increased D2-receptor availability in RLS may correspond to higher receptor densities or lower levels of endogenous dopamine. Both interpretations are consistent with the hypothesis of hypoactive dopaminergic neurotransmission in RLS, as increased receptor levels can be owing to receptor upregulation in response to low levels of endogenous dopamine. The results do not support variations in dopamine D2-receptor availability as a correlate to the diurnal rhythm of RLS symptoms.

1 Recent studies have suggested that the generation of nitric oxide (NO) and hydrogen peroxide (H202) by islet NO synthase and monoamine oxidase, respectively, may have a regulatory influence on insulin secretory processes. We have investigated the pattern of insulin release from isolated islets of Langerhans in the presence of various pharmacological agents known to perturb the intracellular levels of NO and the oxidation state of SH-groups.2 The NO synthase inhibitor, N0-nitro-L-arginine methyl ester (L-NAME) dose-dependently increased L-arginine-induced insulin release. D-Arginine did not influence L-arginine-induced insulin secretion.However, D-NAME which reportedly has no inhibitory action on NO synthase, modestly increased L-arginine-induced insulin release, but was less effective than L-NAME. High concentrations (10 mM) of D-arginine as well as L-NAME and D-NAME could enhance basal insulin release. 3 The intracellular NO donor, hydroxylamine, dose-dependently inhibited insulin secretion induced by L-arginine and L-arginine + L-NAME.4 Glucose-induced insulin release was increased by NO synthase inhibition (L-NAME) and inhibited by the intracellular NO donor, hydroxylamine. Sydnonimine-I (SIN-1), an extracellular donor of NO and superoxide, induced a modest suppression of glucose-stimulated insulin release. SIN-1 did not influence insulin secretion induced by L-arginine or the adenylate cyclase activator, forskolin. L-arginine or tert-butylhydroperoxide at 3 or 300 gM but was markedly increased (14 fold) by a high hydroxylamine concentration (300 gM). In contrast, islet adenosine 3':5'-cyclic monophosphate (cyclic AMP) content was increased (3 fold) by L-arginine (10 mM) and (2 fold) by tert-butylhydroperoxide (300 gM).7 Our results strongly suggest that NO is a negative modulator of insulin release induced by the nutrient secretagogues L-arginine and glucose. This effect is probably not mediated to any major extent by the guanylate cyclase-cyclic GMP system but may rather be exerted by the S-nitrosylation of critical thiol groups involved in the secretory process. Similarly the inhibitory effect of tert-butylhydroperoxide is likely to be elicited through affecting critical thiol groups. The mechanism underlying the secretionpromoting action of tert-butylhydroperoxide on IBMX-induced insulin release is probably linked to intracellular Ca2'-perturbations affecting exocytosis.8 Taken together with previous data the present results suggest that islet production of low physiological levels of free radicals such as NO and H202 may serve as important modulators of insulin secretory processes.

Triclosan is an antibacterial compound commonly used in cosmetics and personal care products for everyday use. As previously shown, triclosan is found in the plasma, urine and milk from large parts of different human populations. Recent studies have revealed that triclosan is able to activate the human pregnane X receptor in vitro and thus possibly affecting metabolism of drugs in humans via the induction of CYP3A4. Besides, triclosan has been shown to affect thyroid hormonal levels in rats in vivo. In the present study, we investigated if an everyday exposure to triclosan via triclosan-containing toothpaste for 14 days in 12 adult humans caused an increase in plasma 4b-hydroxycholesterol, indicative of CYP3A4 induction, and ⁄ or alterations in thyroid hormonal status. The plasma triclosan concentrations increased from 0.009-0.81 ng ⁄ g to 26-296 ng ⁄ g (ranges) upon exposure. Despite this, there were no significant changes in plasma levels of either plasma 4b-hydroxycholesterol or thyroid hormones during the exposure. This indicates that the normal use of triclosancontaining toothpaste is not likely to alter metabolism of drugs via CYP3A4 induction or cause adverse events because of thyroid disturbances in humans.

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