Effectiveness of a web-based protocol for the screening and phenotyping of individuals with Tourette syndrome for genetic studies

Genome-wide association studies (GWAS) and other emerging technologies offer great promise for the identification of genetic risk factors for complex psychiatric disorders, yet such studies are constrained by the need for large sample sizes. Web-based collection offers a relatively untapped resource for increasing participant recruitment. Therefore, we developed and implemented a novel web-based screening and phenotyping protocol for genetic studies of Tourette syndrome (TS), a childhood-onset neuropsychiatric disorder characterized by motor and vocal tics. Participants were recruited over a 13-month period through the membership of the Tourette Syndrome Association (TSA; n = 28,878). Of the TSA members contacted, 4.3% (1,242) initiated the questionnaire, and 79.5% (987) of these were enrollment eligible. 63.9% (631) of enrolled participants completed the study by submitting phenotypic data and blood specimens. Age was the only variable that predicted study completion; children and young adults were significantly less likely to be study completers than adults 26 and older. Compared to a clinic-based study conducted over the same time period, the web-based method yielded a 60% larger sample. Web-based participants were older and more often female; otherwise, the sample characteristics did not differ significantly. TS diagnoses based on the web-screen demonstrated 100% accuracy compared to those derived from in-depth clinical interviews. Our results suggest that a web-based approach is effective for increasing the sample size for genetic studies of a relatively rare disorder and that our web-based screen is valid for diagnosing TS. Findings from this study should aid in the development of web-based protocols for other disorders.

Using perturbation theory to compute the morphological similarity of diffusion tensors

Computing the morphological similarity of diffusion tensors (DTs) at neighboring voxels within a DT image, or at corresponding locations across different DT images, is a fundamental and ubiquitous operation in the postprocessing of DT images. The morphological similarity of DTs typically has been computed using either the principal directions (PDs) of DTs (i.e., the direction along which water molecules diffuse preferentially) or their tensor elements. Although comparing PDs allows the similarity of one morphological feature of DTs to be visualized directly in eigenspace, this method takes into account only a single eigenvector, and it is therefore sensitive to the presence of noise in the images that can introduce error intothe estimation of that vector. Although comparing tensor elements, rather than PDs, is comparatively more robust to the effects of noise, the individual elements of a given tensor do not directly reflect the diffusion properties of water molecules. We propose a measure for computing the morphological similarity of DTs that uses both their eigenvalues and eigenvectors, and that also accounts for the noise levels present in DT images. Our measure presupposes that DTs in a homogeneous region within or across DT images are random perturbations of one another in the presence of noise. The similarity values that are computed using our method are smooth (in the sense that small changes in eigenvalues and eigenvectors cause only small changes in similarity), and they are symmetric when differences in eigenvalues and eigenvectors are also symmetric. In addition, our method does not presuppose that the corresponding eigenvectors across two DTs have been identified accurately, an assumption that is problematic in the presence of noise. Because we compute the similarity between DTs using their eigenspace components, our similarity measure relates directly to both the magnitude and the direction of the diffusion of water molecules. The favorable performance characteristics of our measure offer the prospect of substantially improving additional postprocessing operations that are commonly performed on DTI datasets, such as image segmentation, fiber tracking, noise filtering, and spatial normalization.

Dissociative attachment to ClCN and BrCN

We present calculated dissociative attachment cross sections for ClCN and BrCN in the 0-20 eV energy range. In this energy region, both Cl(-)Br(-) and CN(-) fragments are possible and are produced via dissociation along repulsive resonance curves. Electron scattering calculations, using the complex Kohn variational method and molecular structure calculations, were used to determine the three-dimensional surfaces and resonance parameters. The nuclear dynamics was studied in one, two, and three dimensions using time-dependent wave packet methods, employing the multiconfiguration time-dependent Hartree method for multiple dimensions. The calculated cross sections are reported and compared to the available experiments. Couplings between resonance states will also be examined and discussed.

Interaction of iron deficiency and lead and the hematologic findings in children with severe lead poisoning

Microcytic anemia, long considered an effect of lead poisoning, may in fact result from coexisting iron deficiency. In this study, how RBC size, hemoglobin, and zinc protoporphyrin vary as a function of iron status in a group of children with high lead levels was examined. Charts of all children (N = 51) admitted to Cook County Hospital for treatment of lead poisoning in 1981 to 1983 were reviewed for data on age, blood lead level, hemoglobin concentration, MCV, transferrin saturation and zinc protoporphyrin level. The mean lead level was 86 micrograms/dL and the range was 63 to 190 micrograms/dL. Children with transferrin saturation values less than 7% had a mean MCV of 56 microL, hemoglobin of 8.9 g/dL, and zinc protoporphyrin of 693 micrograms/dL; for those with saturations of 7% to 16%, the values were 61 microL, 10.1 g/dL, and 581 micrograms/dL, respectively; the children with saturations greater than 16% had normal mean MCVs and hemoglobin concentrations (74 microL and 11.4 g/dL) and a mean zinc protoporphyrin value of 240 micrograms/dL (P less than .0005). Multiple linear regression was used to correct for effect of age, and transferrin saturation remained the most important predictor of MCV, hemoglobin, and zinc protoporphyrin levels; the addition of lead did not improve the models. Results of this study suggest that iron deficiency is strongly associated with some of the observed toxicities of lead. Also, lead poisoning can exist without producing microcytosis or anemia, and zinc protoporphyrin concentration may not be a sensitive indicator of lead level in the absence of iron deficiency.