Unusual Particles in Splenic Disorders

Virus-like particles have been seen on electronmicroscopic examination of four spleens surgically removed for haematological disorders—three cases of idiopathic thrombocytopenic purpura and one case of haemolytic anaemia. The particles were approximately spherical and 50-60 nanometres in diameter.     

The uptake of actinomycin D by normal and virus transformed BHK21 hamster cells

The uptake of actinomycin-D (AMD) in the hamster cell line BHK21 clone 13, and its polyoma virus-transformed derivative, were compared. In the transformed cell the internal AMD concentration at equilibrium was lower and was reached more quickly. The AMD-binding capacities of nuclei from normal and transformed cells were similar, suggesting that some control of AMD uptake occurs at the plasma membrane. This may be a control on the efflux of AMD since this process has a higher rate constant in transformed cells.     

On the analysis of phylogenetically paired designs

As phylogenetically controlled experimental designs become increasingly common in ecology, the need arises for a standardized statistical treatment of these datasets. Phylogenetically paired designs circumvent the need for resolved phylogenies and have been used to compare species groups, particularly in the areas of invasion biology and adaptation. Despite the widespread use of this approach, the statistical analysis of paired designs has not been critically evaluated. We propose a mixed model approach that includes random effects for pair and species. These random effects introduce a “two-layer” compound symmetry variance structure that captures both the correlations between observations on related species within a pair as well as the correlations between the repeated measurements within species. We conducted a simulation study to assess the effect of model misspecification on Type I and II error rates. We also provide an illustrative example with data containing taxonomically similar species and several outcome variables of interest. We found that a mixed model with species and pair as random effects performed better in these phylogenetically explicit simulations than two commonly used reference models (no or single random effect) by optimizing Type I error rates and power. The proposed mixed model produces acceptable Type I and II error rates despite the absence of a phylogenetic tree. This design can be generalized to a variety of datasets to analyze repeated measurements in clusters of related subjects/species.