On the interpretation of removable interactions: A survey of the field 33 years after Loftus

In a classic 1978 Memory &Cognition article, Geoff Loftus explained why noncrossover interactions are removable. These removable interactions are tied to the scale of measurement for the dependent variable and therefore do not allow unambiguous conclusions about latent psychological processes. In the present article, we present concrete examples of how this insight helps prevent experimental psychologists from drawing incorrect conclusions about the effects of forgetting and aging. In addition, we extend the Loftus classification scheme for interactions to include those on the cusp between removable and nonremovable. Finally, we use various methods (i.e., a study of citation histories, a questionnaire for psychology students and faculty members, an analysis of statistical textbooks, and a review of articles published in the 2008 issue of Psychology andAging) to show that experimental psychologists have remained generally unaware of the concept of removable interactions. We conclude that there is more to interactions in a 2 × 2 design than meets the eye

Multiple Genotypes of Influenza B Virus Circulated between 1979 and 2003

The segmented genome of influenza B virus allows exchange of gene segments between cocirculating strains. Through this process of reassortment, diversity is generated by the mixing of genes between viruses that differ in one or more gene segments. Phylogenetic and evolutionary analyses of all 11 genes of 31 influenza B viruses isolated from 1979 to 2003 were used to study the evolution of whole genomes. All 11 genes diverged into two new lineages prior to 1987. All genes except the NS1 gene were undergoing linear evolution, although the rate of evolution and the degree to which nucleotide changes translated into amino acid changes varied between lineages and by gene. Frequent reassortment generated 14 different genotypes distinct from the gene constellation of viruses circulating prior to 1979. Multiple genotypes cocirculated in some locations, and a sequence of reassortment events over time could not be established. The surprising diversity of the viruses, unrestricted mixing of lineages, and lack of evidence for coevolution of gene segments do not support the hypothesis that the reassortment process is driven by selection for functional differences

Contribution of Vaccine-Induced Immunity toward either the HA or the NA Component of Influenza Viruses Limits Secondary Bacterial Complications▿

Secondary bacterial infections contribute to morbidity and mortality from influenza. Vaccine effectiveness is typically assessed using prevention of influenza, not secondary infections, as an endpoint. We vaccinated mice with formalin-inactivated influenza virus vaccine preparations containing disparate HA and NA proteins and demonstrated an ability to induce the appropriate anti-HA and anti-NA immune profiles. Protection from both primary viral and secondary bacterial infection was demonstrated with vaccine-induced immunity directed toward either the HA or the NA. This finding suggests that immunity toward the NA component of the virion is desirable and should be considered in generation of influenza vaccines

Treatment with Lysin Eliminates Colonization and Prevents the Development of Otitis Media

<div><p>(A–B) Mice were colonized intranasally with 1 × 10⁵ CFU of S. pneumoniae and seven days later were infected with influenza virus. Four hours prior to viral infection, and then again at the time of viral infection, mice were either (A) treated intranasally with 1,000 μg of Cpl-1 lysin suspended in 20 μl of enzyme buffer⁴, or (B) mock treated with 20 μl of enzyme buffer. Mice were imaged for 60 seconds daily. (A) A representative mouse mock-treated with enzyme buffer develops bilateral otitis media 24 hours after infection with influenza virus, while (B) a representative mouse treated with lysin clears the colonizing pneumococci and does not develop a secondary bacterial infection.</p><p>(C) Although colonization of mice on day 7 did not differ between the groups (<i>p</i> = 1.00), significantly fewer mice treated with Cpl-1 remained colonized 24 hours later (<i>p</i> = 0.00012), and no treated mice developed otitis media compared to mock-treated animals, in which otitis media was seen in 80% (<i>p</i> = 0.00036). An asterisk indicates a significant difference between the groups using a 2-tailed Fisher's Exact test.</p></div

Visualization of Bioluminescent Bacteria Inside Live, Anesthetized Animals Shows the Induction of Otitis Media

<div><p>(A–B) Six- to eight-week-old female Balb/cJ mice (Jackson Laboratory, <a href="http://www.jax.org" target="_blank">http://www.jax.org</a>) were colonized intranasally with 1 × 10⁵ CFU of type 19F S. pneumoniae strain ST162^19F suspended in 100 μl of sterile PBS, then seven days later either (A) infected intranasally in a volume of 100 μl of sterile PBS with 100 TCID₅₀ (doses of virus infectious for 50% of tissue culture wells) of the Mount Sinai strain of influenza virus A/Puerto Rico/8/34 (H1N1), or (B) mock-infected with sterile PBS. Mice were imaged for 60 seconds daily using an IVIS Lumina Imaging System (Xenogen, <a href="http://www.xenogen.com" target="_blank">http://www.xenogen.com</a>), and images were analyzed using Living Image software (version 2.50.1, Xenogen). (A) Pneumococcal load in the nose of a representative mouse colonized with pneumococcus remained the same after mock-infection with PBS, while (B) a representative mouse infected with influenza virus developed otitis media in the left ear.</p><p>(C) Although colonization of mice on day 7 did not differ between the groups (<i>p</i> = 0.56), significantly more mice infected with influenza developed otitis media than did mock-infected animals (<i>p</i> = 0.00053). An asterisk indicates a significant difference between the groups using a 2-tailed Fisher's Exact test.</p></div