Combining insights from quantile and ordinal regression: Child malnutrition in Guatemala

Chronic child undernutrition is a persistent problem in developing countries and has been the focus of hundreds of studies where the primary intent is to improve targeting of public health and economic development policies. In national level cross-sectional studies undernutrition is measured as child stunting and the goal is to assess differences in prevalence among population subgroups. Several types of regression modeling frameworks have been used to study childhood stunting but the literature provides little guidance in terms of statistical properties and the ease with which the results can be communicated to the policy community. We compare the results from quantile regression and ordinal regression models. The two frameworks can be linked analytically and together yield complementary insights. We find that reflecting on interpretations from both models leads to a more thorough analysis and forces the analyst to consider the policy utility of the findings. Guatemala is used as the country focus for the study.     

Mouse Ifit1b is a cap1-RNA–binding protein that inhibits mouse coronavirus translation and is regulated by complexing with Ifit1c

Knockout mouse models have been extensively used to study the antiviral activity of IFIT (interferon-induced protein with tetratricopeptide repeats). Human IFIT1 binds to cap0 (m7GpppN) RNA, which lacks methylation on the first and second cap-proximal nucleotides (cap1, m7GpppNm, and cap2, m7GpppNmNm, respectively). These modifications are signatures of “self” in higher eukaryotes, whereas unmodified cap0-RNA is recognized as foreign and, therefore, potentially harmful to the host cell. IFIT1 inhibits translation at the initiation stage by competing with the cap-binding initiation factor complex, eIF4F, restricting infection by certain viruses that possess “nonself” cap0-mRNAs. However, in mice and other rodents, the IFIT1 orthologue has been lost, and the closely related Ifit1b has been duplicated twice, yielding three paralogues: Ifit1, Ifit1b, and Ifit1c. Although murine Ifit1 is similar to human IFIT1 in its cap0-RNA–binding selectivity, the roles of Ifit1b and Ifit1c are unknown. Here, we found that Ifit1b preferentially binds to cap1-RNA, whereas binding is much weaker to cap0- and cap2-RNA. In murine cells, we show that Ifit1b can modulate host translation and restrict WT mouse coronavirus infection. We found that Ifit1c acts as a stimulatory cofactor for both Ifit1 and Ifit1b, promoting their translation inhibition. In this way, Ifit1c acts in an analogous fashion to human IFIT3, which is a cofactor to human IFIT1. This work clarifies similarities and differences between the human and murine IFIT families to facilitate better design and interpretation of mouse models of human infection and sheds light on the evolutionary plasticity of the IFIT family.     

Intermediate host for an Amblyospora sp. (microspora) infecting the mosquito, Culex annulirostris

Experiments conducted in Australia are described which show that there is an intermediate host involved in the life cycle of an Amblyospora sp. infecting the mosquito, Culex annulirostris. Microsporidian spores produced in the cyclopoid copepod, Mesocyclops albicans, are infectious to laboratory colony C. annulirostris larvae and produce developmental stages identical to those of natural Amblyospora infections in this mosquito. These larval infections result in uninucleate spores in progeny mosquitoes which, in turn, are infectious to M. albicans. Subsequent studies conducted with Amblyospora, copepods, and mosquitoes in the United States to replicate and reconfirm results obtained in Australia were successful. This is the first substantiated evidence of the involvement of intermediate hosts in the life cycles of microsporidia, and the discovery now provides us with information needed to evaluate these organisms as biological control agents for mosquitoes and other disease vectors.     

The Action Spectrum for Shifting the Phase of the Rhythm of Luminescence in Gonyaulax polyedra

The action spectrum for changing the phase of the rhythm of luminescence in the marine dinoflagellate Gonyaulax polyedra has been determined. Maxima in effectiveness were found at 475 and 650 mµ. The significance of these findings is discussed.     

Restraining hamsters alters their breathing pattern

Does the restraint required for head or nose-only exposure of rodents to inhaled aerosols or gases alter their breathing pattern? And does prior exercise training, which may increase muscle strength, affect this response to restraint? To answer those questions, we measured breathing pattern in 11 adult male hamsters while they were either 1) free to move in small cages or 2) closely restrained in head-out cones. The measurements were repeated after hamsters spent 6 wk either sedentary in standard cages or in cages with exercise wheels. Hamsters were placed in a plethysmograph to measure respiratory frequency (f) and tidal volume (VT). Their product is minute volume (V). When restrained, f and V were 1.9 and 1.7 times, respectively, greater than when hamsters were free, but VT did not change. After 6 wk, the sedentary group responded differently to restraint; f increased 3-fold, VT decreased by one-half, and V increased 1.6-fold. Exercised hamsters increased f 2.3-fold and decreased VT by one-third; V increased by 1.5-fold. In inhalation studies, changes in breathing pattern would significantly influence the amount of material inhaled, the fraction retained, and thus the amount and distribution of material deposited in the lungs.     

Crypticola clavulifera gen. et sp. nov. and Lagenidium giganteum: oomycetes pathogenic for dipterans infesting leaf axils in an Australian rain forest

The isolation of two entomopathogenic fungi from Forcipomyia marksae larvae collected in leaf axils of Colocasia macrorrhiza in northeastern Queensland rain forests is reported. An oomycete, in which the zoospores complete their development wholly within the sporangium and are discharged through a short papillar extension, is described as a new genus and species, Crypticola clavulifera. A strain of the well-known oomycete, Lagenidium giganteum, was isolated from F. marksae--the first record of this fungus infecting a member of the Ceratopogonidae. The pathogenesis and zoosporogenesis of the two fungi in mosquito and ceratopogonid larvae are described.