Anxiety and threat-related attentional biases in adolescents with fragile X syndrome.

BACKGROUND: Fragile X syndrome (FXS) is a single-gene disorder highly associated with anxiety; however, measuring anxiety symptoms in FXS and other neurogenetic syndromes is challenged by common limitations in language, self-awareness and cognitive skills required for many traditional assessment tasks. Prior studies have documented group-level differences in threat-related attentional biases, assessed via eye tracking, in FXS and non-FXS groups. The present study built on this work to test whether attentional biases correspond to clinical features of anxiety among adolescents and young adults with FXS. METHODS: Participants included 21 male adolescents with FXS ages 15-20 years who completed an adapted eye-tracking task that measured attentional bias towards fearful faces of varied emotional intensity. RESULTS: Among participants without anxiety disorders, attentional bias towards fear increased across age, similar to non-FXS paediatric anxiety samples. In contrast, participants with anxiety disorders exhibited greater stability in fear-related attentional biases across age. Across analyses, subtle fear stimuli were more sensitive to within-group anxiety variability than full-intensity stimuli. CONCLUSIONS: Our results provide novel evidence that although threat-related attentional biases may correspond with anxiety outcomes in FXS, these associations are complex and vary across developmental and task factors. Future studies are needed to characterise these associations in more robust longitudinal samples, informing whether and how eye-tracking tasks might be optimised to reliably predict and track anxiety in FXS.

Amino Acid Metabolism of Lemna minor L. : II. Responses to Chlorsulfuron.

Chlorsulfuron, an inhibitor of acetolactate synthase (EC 4.1.3.18) (TB Ray 1984 Plant Physiol 75: 827-831), markedly inhibited the growth of Lemna minor at concentrations of 10(-8) molar and above, but had no inhibitory effects on growth at 10(-9) molar. At growth inhibitory concentrations, chlorsulfuron caused a pronounced increase in total free amino acid levels within 24 hours. Valine, leucine, and isoleucine, however, became smaller percentages of the total free amino acid pool as the concentration of chlorsulfuron was increased. At concentrations of chlorsulfuron of 10(-8) molar and above, a new amino acid was accumulated in the free pool. This amino acid was identified as alpha-amino-n-butyrate by chemical ionization and electron impact gas chromatography-mass spectrometry. The amount of alpha-amino-n-butyrate increased from undetectable levels in untreated plants, to as high as 840 nanomoles per gram fresh weight (2.44% of the total free pool) in plants treated with 10(-4) molar chlorsulfuron for 24 hours. The accumulation of this amino acid was completely inhibited by methionine sulfoximine. Chlorsulfuron did not inhibit the methionine sulfoximine induced accumulations of valine, leucine, and isoleucine, supporting the idea that the accumulation of the branched-chain amino acids in methionine sulfoximine treated plants is the result of protein turnover rather than enhanced synthesis. Protein turnover may be primarily responsible for the failure to achieve complete depletion of valine, leucine, and isoleucine even at concentrations of chlorsulfuron some 10(4) times greater than that required to inhibit growth. Tracer studies with (15)N demonstrate that chlorsulfuron inhibits the incorporation of (15)N into valine, leucine, and isoleucine. The alpha-amino-n-butyrate accumulated in the presence of chlorsulfuron and [(15)N]H(4) (+) was heavily labeled with (15)N at early time points and appeared to be derived by transamination from a rapidly labeled amino acid such as glutamate or alanine. We propose that chlorsulfuron inhibition of acetolactate synthase may lead to accumulation of 2-oxobutyrate in the isoleucine branch of the pathway, and transamination of 2-oxobutyrate to alpha-amino-n-butyrate by a constitutive transaminase utilizing either glutamate or alanine as alpha-amino-N donors.