Genome Sequence of the Pea Aphid Acyrthosiphon pisum

Aphids are important agricultural pests and also biological models for studies of insect-plant interactions, symbiosis, virus vectoring, and the developmental causes of extreme phenotypic plasticity. Here we present the 464 Mb draft genome assembly of the pea aphid Acyrthosiphon pisum. This first published whole genome sequence of a basal hemimetabolous insect provides an outgroup to the multiple published genomes of holometabolous insects. Pea aphids are host-plant specialists, they can reproduce both sexually and asexually, and they have coevolved with an obligate bacterial symbiont. Here we highlight findings from whole genome analysis that may be related to these unusual biological features. These findings include discovery of extensive gene duplication in more than 2000 gene families as well as loss of evolutionarily conserved genes. Gene family expansions relative to other published genomes include genes involved in chromatin modification, miRNA synthesis, and sugar transport. Gene losses include genes central to the IMD immune pathway, selenoprotein utilization, purine salvage, and the entire urea cycle. The pea aphid genome reveals that only a limited number of genes have been acquired from bacteria; thus the reduced gene count of Buchnera does not reflect gene transfer to the host genome. The inventory of metabolic genes in the pea aphid genome suggests that there is extensive metabolite exchange between the aphid and Buchnera, including sharing of amino acid biosynthesis between the aphid and Buchnera. The pea aphid genome provides a foundation for post-genomic studies of fundamental biological questions and applied agricultural problems

Conformational Polymorphism: The Missing Phase of 1,1,2,2-Tetrachloroethane (Cl₂HC–CHCl₂)

Halogenoethane derivatives are known to exhibit different polymorphs involving a different translational, orientational, and conformational order. The 1,1,2,2-tetrachloroethane (Cl₂HC–CHCl₂) exhibits a normal pressure orthorhombic phase β (space group <i>P</i>2₁2₁2₁ with <i>Z</i> = 8 and <i>Z</i>′ = 2), formed by molecules with one of the two <i>gauche</i> conformations. At high pressure, the stable polymorph is known to be monoclinic (space group <i>P</i>2₁/<i>c</i>, with <i>Z</i> = 2 and <i>Z</i>′ = 0.5), phase α, in which only the <i>trans</i> conformer appears. In this work, we demonstrate the existence of a normal pressure metastable polymorph, phase γ, for which the two <i>gauche</i> conformers show up in the asymmetric unit of a monoclinic (space group <i>P</i>2₁/<i>c</i> with <i>Z</i> = 8 and <i>Z</i>′ = 2) structure. The new phase γ is obtained by recrystallization upon heating the glass obtained after quench of the melt. It displays shorter type II Cl···Cl contacts than the high-pressure phase α due to attractive and directional interactions

Neurologic signs in young children with human immunodeficiency virus infection

Neurologic and neurodevelopmental problems were investigated in a cohort of 39 human immunodeficiency virus (HIV)-infected children and 164 antibody-negative children born to HIV-positive women. All children were followed from birth for between 1 month and 4 years. Serious neurologic manifestations were present in 5 of 16 children (31%) who developed acquired immunodeficiency syndrome/acquired immunodeficiency syndrome-related complex, although in 2 the neurologic signs were probably not related to HIV. This can be compared with a prevalence of 0 of 23 in children who remained asymptomatic or who had less severe HIV-related symptoms or signs and 2 of 164 (1%) in uninfected children. Neurologic signs in the uninfected group were associated with the presence of drug withdrawal at birth and prematurity. These findings contrast with reports of a high prevalence of neurologic findings in most studies of HIV-infected children

Level and pattern of HIV-1-RNA viral load over age: Differences between girls and boys?

Objective: To estimate RNA viral load patterns over age in vertically infected children that account for between- and within-individual variation, treatment and assay cut-off detection level. To investigate possible sex-based differences. Design: A total of 118 infected children with 894 RNA viral load measurements enrolled in the European Collaborative Study were prospectively followed from birth for up to 15 years. Methods: Fractional polynomial and mixed effects models with censored data to assess the non-linear pattern of viral load over age, allowing for repeated measures. Results: The RNA viral load peaked at approximately 3 months of age, and gradually declined thereafter. The sex by age interaction was significant (X2 = 19.7, P &lt; 0.001); viral load peaked higher for girls than boys, but after 4 years the RNA load was consistently 0.25-0.5 log10 lower for girls than boys. The effects of sex and treatment on viral load vary over age (X2 = 6.31, P = 0.043). Sex differences in RNA viral load relating to measurement without treatment were more pronounced than those under treatment. Disease progression was more rapid for girls than for boys up to the age of 4 years, and less rapid thereafter; the overall difference was not statistically significant. Conclusion: Differences in RNA viral load over age between untreated boys and girls may have implications for policies for the initiation of antiretroviral therapy, but do not seem to translate into differences in progression to serious disease. The findings would suggest underlying biological explanations, which need further investigation